iPhone 5 or an HTC One (M7)?

I want to buy an iPhone 5 as my secondary phone, but somebody told me that I should get an M7 instead as the price difference is negligible with One being a little cheaper. It's practically a pretty beautiful device and the only thing stopping me from buying it, is my fear of UI lags.

I tried Android when ICS came out and iOS could beat it hands down then. in fluidity of animations and response times. All I want to ask is, if M7 would be any better than and iPhone 5, camera isn't my concern the only thing I care about is that it should have a smooth user experience and no lags.

Any idea fellas?