I would definitely want Brent Grimes over Aqib Talib and it's not even close. He's a better cornerback Grimes has never had any league suspensions whereas Talib is always one dumb move away from missing the season (whether it be from off field stupidity or drug use). I know Grimes is coming off a major injury and is 30 years old, but I think that by the end of the season he is back to his original form, as he was injured early in the season last year. Getting Grimes now would be getting a very good to elite player at a time where his market is depressed. There is a reason he was franchised last season and when healthy I'm not sure that there are 5 CB's better than he is.
I just don't see the justification for giving Talib a big contract right now. He played well in a few games for the Patriots, but due to suspension and injury he only played 9 games last season. I do think he matches up well with big, physical receivers. However, both A Johnson and especially A Boldin have lost a few steps over the years. My concern is that Talib doesn't match up overly well with faster receivers.