I own the Arturia V6 Collection and i really do like it, i think the Piano is really not the worst you might find on the market and so is the organ… but the majority of plugins consists of the vintage synths, and that’s what you mainly pay for. Amongst those synths are a few CPU-hogs (like the Buchla Easel), but most of them play very well on my i7/16GB. As far as i remember, the CPU load from the Piano and Organ is quite moderate.
So, i would say if you do not really need or want the vintage Synths then go for the Pianoteq VST, since you already have the NI Complete which also comes with a lot of (vintage)Synths…