I'd readily admit to being out of the loop with what's going on domestically but I've never known Robshaw to let England down, he's been remarkably consistent for England in that he never really drops below an 85% performance level, although his ceiling is lower than some, I'm not sure that it's below the two mentioned. Hughes particularly is like a powder puff at international level.
All that being said, if everyone is fit, I'd like to see Billy, Underhill, Curry and Wilson as the starting/bench back row.
In a wider squad there's room for Robshaw IMO, same as there is for Hartley, Care and Brown. It seems silly just to jettison all of that experience. As others have mentioned, I'd also like to see Morgan back involved with England he has infinitely more to offer than Hughes.