Among them (but not necesarily all):
- HiPower has no removeable barrel bushing or swinging barrel link; also no grip safety.
- HiPower has a magazine safety (won't fire if mag is out)
- Most HiPowers (being 9mm) have hi-capacity, double-stack magazines; most 1911s are single stack .45s.
- Trigger linkage is totally different; 1911 goes straight back, with stirrup on either side of magazine, to activate sear; on HiPower, trigger action pushes up, pushing on a lever in the slide above, which pushes down on the sear behind the magazine.
- As a general, esthetic thing, where the HiPower has a double-stack mag in a smaller caliber, it's thicker in the grip and thinner in the slide/barrel; whereas the 1911 tends to be the same thickness from grip to barrel (that's why it's sometimes called "old slabsides").
HTH. Peter F.