Personally, for myself I'd get the Ixus 95IS, but for the average person the A1100 would probably be a better choice because, as the others have said, it can zoom in further, which is the kind of thing that people take note of in a camera

I'd prefer the Ixus cause it's smaller and lighter, so I'd be much more likely to carry it around and actually use it.
Main differences:
- A1100 has 12mp, the 95IS has 10mp. Unless the person is going to crop their photos a lot, or make huge (bigger than A3) prints, they probably won't notice the difference.
- The A1100 has the equivalent of a 35-140mm lens, the 95IS 35-105mm. This means that the A1100 can zoom in further. They're both the same at the wide angle end
- They both have a 2.5" screen, but the 95IS has 230k pixels vs the A1100's 115k
- The apertures are more or less the same, f/2.7-5.6 vs f/2.8-4.9
- Important: The A1100 takes 2x AA batteries, the 95IS uses Canon Li-on ones
- The A1100 is 95x62x31mm, the 95IS is 88x54x21. Considerably thinner
- The A1100 is 155g, the 95IS is 120g
Other notes: (not really important, you can skip this, I'm bored and just rambling on)
- They have the same size sensor (1/2.3")
- They both go from ISO80 to 1600, and probably have the same high ISO performance
- While the 95IS can't zoom as far on the long end, it has 1x double and 1x single sided aspherical element compared to the A1100's 2x single sided, so it might have less chromatic abberation.
- The 95 IS has 6 elements compared to the A1100's 7, so it MIGHT have marginally (not noticeable in real life) less flare
- It also has a shorter range of focal length, so you MIGHT get less barrel and pincushion distortion at the wide and long ends respectively.
I'd decide based on (in descending importance):
What I'd base the decision on:
1. Will they need the extra zoom?
2. Does the size matter to them?
3. Do they prefer AA or proprietary Canon batteries?
PowerShot A1100 IS specifications
IXUS 95 IS specifications