MacBook Air :: Making The Switch, But To The Mba Or Mbp?

i know you've already tackled this a thousand times, but, having read those thousand threads, i'm still not sure which of these i should go for. you all seem generous with your opinions, so i'll ask again.i need to replace my 4 year old dell 700m (12.1", 1.6ghz, 512mb ram, tiny 24gb HD) as it has become painfully slow and things are beginning to stop working. i've very much enjoyed its portability (it's small and weighs just over 4 pounds) which is why the MBA has caught my eye. my concern, is that i've heard all these things about it being underpowered - but underpowered for what? the lure of the MBP, of course, is that it's a lot more power for its moderate increase in bulk and weight.