Some years ago a friend said to me something like "you know the Hi-Power was designed to correct all of the faults of the creaky old Government model.  In fact, didn't the Hi-Power officially obsolete the 1911?"  An interesting question, isn't it?   I think the Hi-Power did offer several improvements over the 1911, at least one poor change, and others that are debatable.  Here's how I see some of the differences, starting at the muzzle: 

The lack of a removable barrel bushing in the Hi-Power makes disassembly much easier.  On the other hand you can replace a worn bushing on a 1911 to bring back accuracy, and new barrels are easier to fit to a bushing than to a slide.   I like the bushing, but it is interesting to note that they are almost non-existent in modern designs.

The Hi-Power's integral barrel cam is a stronger arrangement than the 1911's swinging link.  But you can replace the link to effect tighter barrel lock-up rather easily.  The one piece barrel ramp of the Hi-Power must be considered a real improvement.  It greatly simplifies tuning the pistol, if tuning is even required on a Hi-Power.  It also provides better support, which is needed with the higher pressure rounds for which the Hi-Power is chambered.  (Yes, 1911s are now offered with integral barrel ramps, but the original was not, and most still don't come that way.)  And the fact that the Hi-Power's cam rides on a fixed steel cross-pin rather than on the slide lock pin on the 1911 makes for a stronger arrangement.

The excessive take-up in a Hi-Power trigger is something I dislike.  It is hard to improve on the feel of a 1911 trigger with very little take-up and minimal overtravel.  The Hi-Power's up-and-over trigger linkage has been criticized.  I'm not sure why.  It is a little complicated.  On the other hand it works, and Hi-Powers are capable of good trigger pulls.  And the Hi-Power eliminates the separate disconnector of the 1911.  Another advantage is the fact that the sear is bigger and stronger and has no cut-out in it for a non-existent separate disconnector.

The location of the 1911 safety lock is perfect.  (Most folks call it a thumb safety.)  The original location, shape, and size of the Hi-Power's safety was a step backward, as it did not fall naturally under most thumbs.   Forward extending levers as seen on modern Hi-Powers are an improvement.  Jeff Cooper claimed John Browning didn't understand that manipulation of the safety was part of the draw and firing stroke and that was why the safety was changed for the worse.  Unfortunately that isn't the case, as the prototype that Browning designed and which eventually became the Hi-Power did not have this or any safety lever in the conventional place.  The original M1935 Hi-Power safety must be attributed to Dieudonne Saive, FN's chief designer at the time, and the man who really designed the Hi-Power.  One plus of the Hi-Power safety is that it can be locked into a second slot on the slide located forward of the usual safety locking location.  When the slide is locked into this position the slide lock can be pushed out of the gun, and when the safety lock is pushed back down the slide will slip off the front of the frame.  Very simple and convenient disassembly.

The double column Hi-Power magazine is a better design in that the baseplate is removable, making the mag easier to clean.  And I'm sure many of you have had a welded baseplate on a 1911 mag break on you.  It is also easier to seat the Hi-Power magazine without ever getting pinched because it extends past the edges of the mag well.  The double stack aspect of the mag is not significant to me as they haven't made a double stack .45 mag that will result in a truly comfortable grip.*  (And no, I don't think the Para-Ordnance compares favorably to the feel of a Hi-Power or a 1911, not even the latest, thinnest models.)

The addition of a magazine disconnect safety on the Hi-Power is curious.  Some like it, some think it unnecessary.  Fortunately it is simple to remove if one is so inclined.

The short grip tang of the Hi-Power means that some shooters get bitten on the web of their shooting hand by the hammer spur or pinched between hammer and tang.  This is something that would be so basic and simple to change at the factory that there is no reason it still exists in original form.  There are other options besides lengthening the tang, however.  The spur hammer can be shortened or undercut, or a rowel hammer can be fitted--these generally bite or pinch less than the spur hammer.  I don't get bit, so it's no big deal to me.  Improvement-wise, I'd say there is no winner here as Browning's original M1911 tang was no great shakes either and causes many shooters to get bit as well.

The lack of a grip safety on the Hi-Power is an improvement.  It was never needed.  It was added to the original Browning 1911 design at the request of Army Ordnance who envisioned cavalry troopers handling cocked and unlocked M1911s in horseback.

The cartridge is where it really matters to a lot of folks.  In 1974 Cooper said that the Hi-Power can never replace the 1911 because a 9mm doesn't hit hard enough.  Today we have 9mm ammo that can do the job.  It may not be ideal but we shouldn't get hung up on this.  No handgun cartridge is truly "big medicine."  And though I'd prefer a .45, modern 9mm loads beat anything around when Cooper made that comment, so cartridge comparison is not as significant anymore.  And...the .40S&W version of the Hi-Power pretty much solves the cartridge problem, if you see the 9mm as a problem.

By the way, that begs the question "is the .40S&W Hi-Power the same pistol as the 9mm?"  Basically yes, but it is bigger, if not in any significantly measurable way other than weight: the .40HP is 35oz, the 9mm is 32oz.  But it feels bigger.  That's the word; it just doesn't quite feel the same in one's hand, and it handles and shoots a little different, too.  Is this bad?  No, just different.  1911 and Hi-Power fans shouldn't mind too much, as the .40 HP feels something like a Commander slide on a Hi-Power frame.

I am a big fan of both the 1911 and Hi-Power and have several of each.  Which do I prefer?  Probably the .40S&W version of the Hi-Power, which seems the best of both worlds to me.**  It is significantly strengthened over the 9mm version, and it handles the moderately large, high pressure .40S&W cartridge quite well.  The Browning pistol in .40 is the best factory Hi-Power ever made.  It has good, high visibility, drift adjustable sights front and rear.  My only complaint was the current ambidextrous safety levers.  While they are better than Hi-Power safeties in previous times, I just didn't like them, and my personal example wears a single-side safety lever from Cylinder & Slide.

* at the time this was written, just a few short years ago, the double stack .45ACP was represented by a few oversize pistols that were not terribly popular.  Today that has changed as the Springfield XD and the Taurus 24-7, both in .45ACP, have shown the world that a double stack .45ACP is not that hard to do right!  (Later addition: the Glock 21SF is a further excellent double stack .45ACP!)

** In 2007 I must say that I like both the M1911 and the Hi-Power equally well.  I no longer own the .40S&W Hi-Power, only a 9mm, and for the record I don't carry either.  Plastic pistols, striker-fired pistols, and pistols equipped with light, constant-pressure triggers that don't require manipulating a safety have replaced both of these oldies but goodies as my carry guns.

*** I have long since returned to the 1911 as a carry gun, probably around 2012.