Grado bass is very articulate, clean and accurate...part of the reason why I love them...but they won't extend as deep as other options. Imaging is often spot on, and sound stage is natural, but not "large". They are typically airy and will give you tons of detail, and they are among the best headphones you can buy in terms of timbre and tonality. Comfort level is really up in the air depending on whose wearing them. Personally I've never had any complaint at all about their comfort, especially after throwing my ear pads in with the wash (with fabric softener). My SR80s are extremely comfortable as a result...cant even tell they are on my head.
So basically, if you want a large sound stage and/or you prefer an emphasized low end, I'd consider the Senns you mentioned or other options. If you want headphones that are very detailed and airy, on the bright side of neutral, with very natural sounding bass and timbre, and with stable imaging, then give the Grados a go. Personally, except for those who consider themselves bass heads, I really feel that everyone who loves headphones should give Grados an audition at least once.