Phone 2 is position more as a flagship device in the Nothing’s lineup and Phone 2a will be positioned as a mid-rangers. Phone 2 runs on top of the range SoC which is Snapdragon 8+ gen 1 where Phone 2a will run on Mediatek 7200 Pro.
On the paper Snapdragon SoC is more powerful solution for gaming and performance. Comparing then in the Benchmark environment Phone 2 processor comes with about 60% better results than Vanilla Mediatek 7200. I don’t think the Pro version will close that gap significantly.
To conclude, Phone 2a it’s not an upgrade over Phone 2 and the rumoured RRP for the upcoming device will reflect that. It will retail for about €399 in Europe, where Phone 2 is about €500 - €600.