I love my MBP 17" with 1900x resolution. It allows me to pack my screen full. It sounds like it isn't in your budget, but as a developer, you might think about screen real estate. I had a 15" but couldn't develop on it. Since I got this 17", I've used it 100% of the time, 10+ hours a day.
Eh, this needs to be a portable machine, and I fully expect to have an extra monitor available to plug into if I need the real estate for coding. I've simply never needed that much space while on the go. Can't say I'd mind the space, but it's not feasible with my budget. If the Dell Studio 15's were compatible with leopard, I'd go with that because there's a 1900x1200 resolution upgrade that is VERY reasonably priced…
If you regularly plug into a bigger screen, a smaller machine might be better. If the Dell isn't compatible yet, I'm sure it will be in the future. Darn hackers!