Is it running a HTC supplied update?
Obviously not, but i think the point is that any two year old phone will be sluggish, both on iOS and Android. This is truer in Android because the pace of development is that much faster so devices age quicker. Having said that, Android gives you the power to tinker with ROMS, kernels, etc which can add a few more usable years to your device. So unless OP is prepared for this, he should stay in the Apple universe.