well both can be awesome powerplants but as you probably know the 7m's like to blow their stock gaskets... get arp's and a mhg and necessary machine work and the 7m will be reliable if it is maintained
the 1jz is also an awesome powerplant... good power gains can be made with less unreliability issues than the 7m
it's personal preference really... the 1jz is a younger and more advanced motor.. it has great power gains and can handle alot of power stock
the 7m is an older motor but still a great engine... lots of power can be made and they're very torquey
check out
www.7mpower.com for a few looks at 7m's
i'm not sure if there is an equivalent site for the 1jz
good luck on your decision