I mean, 1% is fine if it comes with no other tradeoffs, but that's probably not the case. I would trade a 1% improvement in performance for a 1% improvement in developer productivity almost every single time (very rarely are businesses performance constrained such that they can afford to slow development for marginal performance deltas), and when you're operating near the margins of performance, it's usually more likely that you'll have to halve productivity to eek out a small amount of performance improvement.