Hard to say. When the phase changes, the alpha cards from phase 1 turn into beta cards, and the beta cards are removed. However, the multiplier you got from phase 1 beta cards still counts, so having those would help during phase 2 as well.
On the other hand, I think the alpha cards from phase 2 have a bigger multiplier than the cards from phase 1, so that would be an advantage of those. If you're really short on gacha tickets, I'd save them for phase 2, and hope to get the phase 2 SR.
Do make sure to run the regular N gacha though, just to grab the N card from there (and do it again in Phase 2), with all the other multipliers, it does give a noticable increase!