Thermodynamically speaking, the freezer on bottom ones make the most sense (at least if the coils are on top...).
And this is what several of the appliance guys told me. We're doing a remodel and ended up w/ a KitchenAid bottom fridge. No ice/water in the door because we wanted more interior. It also has an internal water filter which saves us from our monthly Arrowhead delivery.
We don't have it yet but we did do a bit of research. We've had side by side but space is small. You have trouble storing pizza boxes and cakes. The top fridge is probably the most space efficient but for some reason, you don't find high end models. Ours has french doors and steel front, a bit pricey but our local appliance shop is hurting for business and even beat Sears' sales price w/ free delivery. It's a family run shop that's been in business over 40 years. The bottom space is a concern but fortunately, we've got our top fridge going to the garage as a secondary unit. But it does seem that the bottom doesn't have any less space than a side by side would.
You might also check to see if you have a Sears outlet near you. They have LOTS of appliances from their scratch and dent stuff, all below retail and w/ full warranty. If you're lucky, the damage is on the side or back and you save a bunch. One fridge I looked at was about $1K less than the current sale price, but the dent was on the front. My local guy was only a few hundred more so I went w/ him instead.
Beware the Consumer Reports customer reviews. Sometimes people give appliances a really bad rating because of one feature they hate. Then you find that it's a feature you either like or don't care about so the review rating is irrelevant.