KiCad is getting better and better. At this point Altium is copying features _from_ KiCad, so you know the competition is real :).

Altium is still a Delphi-ish program, though with lots of things now just compiling to .Net. The core layout package has always been solid with a very small core developer group running it which is really more what its known for. The library management parts with collaboration are actually getting a lot better (ECAD<->MCAD, etc).

Altium gained tons of weird stuff with a super weird push to "FPGAs for everything", a giant off-shore (not Australian or Carlsbad) development team, and... all of that crash and burned and no actual customer actually understood what was happening. Much of that legacy is still in parts, but most of the features have been removed by now.