The SWAP Striker has higher offensive stats, better multipliers, and notably higher accuracy than the base version, so it can actually hit things. The main downside to this is it costs 6 instead of 4 to put into your echelon.

Almost across the board, it's an improvement for the Vespid. However, its a pain to get a full formation of them because its a 2 star base unit, and as a DPS unit you want it at full stacks. Also, it's not really significantly better than stuff like Jaegers and Strikers. They're not useless, but there are just much better SF units to spend effort and slot points on.