I've never used a 510 besides these disposables, but personally I have pretty much given up my 401 for these. But it's always a matter of personal preference. My only issue now with the 401 is that it's so small, which I used to love about it, but I've gotten used to bigger PVs (901, KR8, and now the 510.) Plus the 401 has a much harder draw. But whatever works for you. Hey, I'm unimpressed with the KR8 cartomizers and most people think they're the greatest thing since the wheel, so don't feel bad!