T2/3 are better connected than T5 and T4 for sure, since they have double the Tube frequency plus both HEX *and* TFL Rail.

However for me the issue isn’t so much about the difference between the terminals, but the poor journey options between Heathrow generally and where I live in fairly central London (Angel). I for one can’t wait for Crossrail. Until then, Luton and Gatwick will remain my preferred airports for shorthaul.