it's not uncommon to use nitrous as a way to cool the turbo boost before it enters the combustion chamber.
If you want to compare pistons, you must first determine the boost you need to get the hp you want (with the necessary factoring in of pressure added by an intercooler and the effect of temp cooling by nitrous). BTW you don't need 125 shot nitrous with a turbo running 9-11 psi boost to cool down the charge.
I think the actual amount of nitrous plays a realtively small role , once boost has been added to making an incremental increase in power...law of diminishing returns.
once you determine the amount of nitrous that will give you the added gain in power on top of the boost you want (50 shot may give you as much as 125 shot once boost has been added), then you select the CR you want to allow that much volume to be shoved into the chamber safely.
it's a trade-off. you add too much nitrous to the boost and the increased temp/pressure inside the chamber will risk more detonation depending on how well atomized the fuel is added and how much fuel is added. So to get a little more at the cost of a huge risk increase in detonation may not be worth it...you have to work out the numbers in detail.
comparing forged pistons, you have to look at the amount of surface area added by the piston top. More surface area reduces the chamber temperature and slows the burn rate and decreases burn efficiency regardless of CR.
if the dish is deeper on one piston compared to another for the same CR, then you have MORE surface area. You don't want that. Some manufacturers give you the lower CR you want without deepening the dish...they reduce the compression height (side profile view of the piston, compression height = distance from the piston pin center to the top of the piston) instead. Just make sure they give you enough top piston ring clearance to the top of the piston for boosted applications.
Weight savings (from using different alloys), larger piston pin diameters (bigger diameters are better), oil drain hole locations, use of free floating rod bushings, a reputation for tight fit to spec, ring end gap, heat coatings on the piston top, low friction coatings on the skirts, and piston skirt length (longer ones rock less as the piston travels up and down) are some other differences you may want to compare when you are shopping.
I see no reason why you should fork over more cash for titanium pistons to get lighter weight and heat resistance. Titanium is an aggressive metal that likes to grab other metals and wear them down faster. Surface incompatibilities are an issue the ti manufacturers don't tell you.
So work out the numbers you need for boost to determine CR you need and then compare the pistons that have that CR using the list of design features to compare...choose the one with the most goodies at a good price.
