The oil feed is the main difference but you also need to decide what Trim as this is also very important and determines the type of bearings, gear set, max rpm, impeller efficiency and ultimately power output.
For the 350z these sc that will fit the std brackets
V2 SC (discontinued): std bearing 52krpm
V3 SCi = V2 SCi = std bearing 53krpm/improved cast impellers rom sc
V2 Si = std bearing 53rpm/more efficient cast impeller
V2 T = HD bearing 55krpm/cast impeller
V1 T = HD bearing but bigger straight cut gears so stronger but noisier than the V2 >V3
V2 Ti (new) = HD bearing 55rpm/ more efficient billet impeller
V1 Ti : as above
V7 YSi = HD race bearing 65krpm/ cast impeller
V7 YSi (new)= HD race bearing 65krpm/ billet impeller
Personally I favour the V2 as it offers superior cooling but others prefer the simplicity of the self lubricated V3. But if you factor in the recommended sc oil changes it's not so simple or cheap.
I have the V2 T trim which I've just sold for the new V7 YSi.