I went with a V6 for several reasons:
1) It was much cheaper to do a starter turbo setup with the current V6 motor. $1700 vs a 3S-GTE swap which could end up being $3500+
2) With my tools and skills at that time, I was only able to do basic fabrication (welding, etc), but I do not have the space to start dropping engines and swapping motors.
3) In the long run, it was about the same price to fully build the 1MZ-FE to go upwards of 500+ HP compared to fully building a 3S-GTE; both motors would need forged internals, machine work, turbos and manifolds, and the same series of fuel/management/electronics/supporting mods and driveline upgrades.
4) You can't beat the advantage of added displacement. Especially on pump gas, you simply cannot make 500-550 WHP on pump gas with a 3S-GTE. The V6 also has a lot more beef to push a big turbo with big numbers so you don't end up with a 1500RPM powerband.
I am a pure V6 guy myself, and unless my Camry came with a 4-cyl, I would never swap to something smaller. 260 WHP on a stock 1MZ-FE (wither bolt-on a TRD SC or a simple turbo kit) is absolutely safe, and you end up having a fat powerband and torque off the line. This is only for the experienced of course, because whenever you have custom tuning involved, you must have someone knowledgeable to set up everything correctly. This could be yourself, or a reputable shop. The next step up approaching 300-350 WHP is when things get expensive.
The cost/HP ratio is about the same between both motors if you are going for big power... There is absolulely minimal price difference if you are building both motors to full extent. Both motors would need identical upgrades from engine to electronics to turbo to driveline. The only problem with the 1MZ-FE is that you'll need custom parts, and without connections to the right people, it can be quite a problem.
A 3S-GTE swap is only cheaper when you are set on a certain power quota. For 300-350 HP, you can't beat a stock bottom 3S-GTE with a slight turbo/fuel upgrade. The simplicity and reliability is the biggest advantage because you are using parts that are tested, tried and true, and most of the tuning is already done for you if you are keeping stock ECU and running stock sensors (ie: stock ECU with basic fuel controller). That's only if you keep it within the power limits.
Lastly the fear factor of having a turbo V6 is nothing but FUN... You wouldn't believe how many guys were shocked whenever I pop up my hood to expose the 3.0L V6 with a huge single. It puts me into the "Supra" territory
