I agree with Tank2, it totally depends on your end goal. If you want to be a Commander in a decent company flying widebody then you're going to have to down grade to F/O (or even S/O) again anyway so why postpone it?
If however you're happy to be flying short haul and jumping around companies who take DECs then take the quick command.
IMHO the command on the E190 would be a far better experience but will it give you the lifestyle and type of flying you want?