I've never used one

how are the chop and sequencing ? compared to a 505 ?

I assume the effects are mostly the same as my 404.. yes ? no ?

hi
try the 606 section,a lot of informations are there.

ps
i have both.
chop is a little bit more complete on the 505 (32 pads dedicated on 505 vs 16 on the 606 + you can move the markers on the 505 during chop function)...
...and editing too: you cannot copy more than one sample (!!!) by clipboard on the 606; you cannot resample other pads than the bank in wich "you are" on the 606.
505 got a sort of picth scale function that 606 doesn't have.
606 can use 2 fx at the same time. 505 can't.
MAIN CONSIDERATION: 505 is a "studio machine" (in the roland/boss sense, anyway), 606 is a machine conceived to work (better) with pc: it's also a soundcard and a midi controller (with software dedicated; but works with every softwares). roland, building the 606, anticipated Maschine.
404 fx are more similar to 303 fx (except the dj looper), i mean the types of fx.

No, 606 has 45 effects and mastering effects. It can also resample external sounds with the internal unlike the 404.

There's only auto-chop but there's ways to manual chop. Check out the 606 section, tons of info.