we have actually done four tubo installs (ludespeed) and four USDM swaps (3 rs's and one OBS)
First and formost you do NOT loose torque by doing a ej20 swap. You loose torque by swapping out the GC tranny for the GD one. The torque is all in the gearing. YOU can keep your stock tranny and use the EJ20 and everything will be ok.
Which has more POWER? better question... How much money are you going to dump into this? IMHO the ej20 has more. there will those that disagree. but oh well.
if you do the swap you will be able to drive away and have the car be smooth from the get go. if you know how and do all the work yourself then plan on spending about 5k for the main componets and then 400-800 for a clutch/flywheel. Then you need to find someone to install it
If you do the turbo kit (2.5-3k) , 1.4k for a link and injectors for $500, fuel pump $200, and 400-800 for a clutch/flywheel combo then you will be able to run somewhat smoothly. Then you still need someone to install and tune it
Bottom line: you want to tinker with your car? then go Turbo kit
you want to drive your car more and worry less about the little things that might not be just right...then go swap.
Like I said I have done both to several cars. some people just wanna drive the dam thing. Others like to be under the hood (engineers).
I frequently see turbo guys becoming disenchanted with their cars because SOMETHING is not right. However, when they fix it...they turn into gitty little girls until something else goes wrong, lol.