I'm Dan91T's roommate. If I were to boost a motor, I'd go LS hands down. With an unlimited budget maybe the GS-R would make a little bit more power, but in the real world with real money, the LS wins big time. You can pick up a great LS full swap with tranny for a grand, the cheaper B18C1's are $3k and C5's are $4.5k.... And then if you blow the motor boosting, you pay that premium again. Basically everything for the GS-R is more expensive - trannies, used parts, cams, etc. And if you break stuff, even more money down the hole. The LS makes comparable, if not more power boosted than a GS-R - why would you spend an extra couple thousand for some gain over the LS that may or may not be realized?
If you wanna talk all motor, it's all about what you want to do with the motor. Drag? GS-R simply because it has great high-end, which is all you really use in drag. Daily driver and autocross? These are both what I want from my car, and in that respect for the money, honestly it beats the shit outta the GS-R. I have spent about $2k on my motor, but the price differential between an LS and GS-R swap is at least that much. I can beat my friend's GS-R with i/h/c/e until 3rd gear (LS 3rd sucks balls) over and over again. I have about 125-130wtq at only 4300rpm, a stock GS-R will only have about 105-108 at 6000rpm, even with i/h/e it will end up with probably 112-118wtq at a similar, if not higher, rpm. My friend's GS-R has slightly better top end than mine but loses until 60mph because of my full powerband. And don't even talk about autocross - his midrange feels gutless compared to mine, mine would obliterate his car on the autocross circuit. I'm not saying my LS is flat-out better than a GS-R, but for certain applications there are advantages, especially when the cash is considered.... All depends on what you wanna do, and of course "how fast you wanna spend".