Generally when I charter for groundfish, I go north of Boston and when I charter stripers, I go south of Boston. For cod I go exclusively with the larger party boats with spacious cabins. For stripers I splurge on a six-pack boat.
I used to use Yankee Fleet. Now I use Captain's Fishing out of Newburyport every year.
http://www.captainsfishing.com/
Staff is always patient and the boat is top notch. Both outfits tend to target Jeffries Ledge. I've been out on Wash's too and have been very impressed. If you want to fish Stellwagen Bank for groundfish, Captain John's is OK and their heated railing is a big plus on the colder days.
Patrick (or anyone else), when was the last time you went out with the Yankee Fleet? Has it been in the past year or two? If so, might be time for me to check them out again.
Mike