I worked at one of large firms in Boston for 5 years before leaving to go in-house. I can comment on my experiences, friends experiences and perception from in-house (because we utilize several Boston firms as outside counsel). This is purely from a corporate perspective:
Ropes - big deals. Some folks get great experience and do well. A lot of corporate associates get lost in the mix or staffed real deep on deals - meaning very little opportunity to take on a lot of responsibility. I met a lot of folks that got a weird mix of corporate experience too so they could do credit agreements, M&A, fund formation, securities...but all at the level of a 1st year and they were a mid-level. It seems like it was feast or famine in terms of the experiences offered from Ropes. Great firm that is well respected in the community, so you can exit to other places if need be, but you may need to make a move to other corporate firms to get solid drafting/deal management experience. The attrition is extremely high and the classes are huge so often times no one knows who you are so they are less likely to invest time in you.
Goodwin - less insight, but I think it is fairly similar to Ropes in terms of the issues I describe above.
No insight into Wilmer or Brown Rudnick - corporate practices are insignificant in my opinion. I've heard most people at BR are miserable though.
Cooley/Weil/Skadden - I'd put in same category for corporate work (although the industries that they service are pretty different). Sophisticated work but tiny offices. Cooley is more tech and Weil is more PE. Skadden is more of a mix but large deals. Personally, I wouldn't want to go to any of these because their offices are too small. They also seemed like sweatshops. I liked working with a broad range of partners because they will each have different practices and different styles - this variety will broaden your skills and make you a better lawyer. Generally speaking, you do not want to just work for one lawyer early on.
Nixon Peabody/Choate/Mintz/
foley hoag: I'd put these in the same category for corporate work. They generally have low partner to associate ratios meaning more substantive work earlier on and probably better training because you interact with the partners more. Deals are smaller, but I view that as a good thing. I always fucking hated any deals north of $500M - there was usually a ton of bullshit paper pushing and diligence. It might grab a headline, but I prefer middle market deals as an associate because you get a chance to run them and you are less likely to need to pull 300+ billable months.
Burns Levinson/Nutter: Slightly below the 4 firms listed above but decent corporate practices that are also leanly staffed.
I don't have much insight into McDermott, H&K or Latham - I didn't have friends at these firms, never worked opposite them on deals and my company doesn't use them for in-house counsel.
If I were targeting firms all over again, I'd prioritize the Nixon Peabody/Choate/Mintz/
foley hoag category. No matter where you go, you are likely to want to leave between years 3-6. At these firms, you are very likely to be running deals by this stage (especially by year 6) and the work is still sophisticated. They are just bigger deals and they have more specialists to pull into the deals. This is type of drafting experience is very important to obtain before moving in-house. I don't think I really appreciated this when I was applying to law firms - I thought that firms like Ropes had deals that were significantly different and more sophisticated than other big firms....they really aren't. Additionally, chances at partnership are much better than a Ropes/Goodwin. Of course, coming out of a Ropes/Goodwin as a 6th year, you might get better looks and have better connections than these firms, but it is highly unlikely you will make it to this level (especially at Ropes).
Apologies for stream of consciousness writing but I can't be bothered to clean it up. If I didn't mention a firm, it's because I had no info on them (probably because their corporate presence is insignificant around Boston). You will get very different cultural feels from each of these firms - once you get a callback, it will be apparent as you talk with people and as you walk through the hallways. Don't overanalyze now unless you need to prioritize bidding.
