2jz is the best choice because you can reach 500hp with little spending and only with single turbo T88 900ccinjectors, head porting, 272 cams and motec or AEM you can reach 840hp c16fuel and 650+hp with 95 octane.
However, the over heat is big problem that I have faced with my swapping the lack of length of bay space is the problem, making it deffecults to install radiator and fans. you have to cut some of radiator support and add spacers for between chassis and bridge and fabricate mounts
for rb25 I have a friend who swapped rb25 he tolled me it is much less then VG in performance and power potential.
check my album
http://forums.hybridz.org/member.php?u=27424