Which internship is better for moving into top L/S: GS NY ER vs. Dodge & Cox ER

If you don't mind being in SF as opposed to NY, then go Dodge & Cox. The funds you mentioned are predominantly NY/Chicago, so there is a slight location disadvantage, but I think D&C is a better summer gig than ER at GS in the general sense. A few cautionary notes, however:

• The intern-to-FT conversion at D&C is on an as-needed basis across three rotations, and the teams you rotate will only hire their first pick out of the interns (if they're hiring at all). The firm is also notorious for forcing out its Research Associates (entry-level FT research role).
• Very few make the jump to the Analyst position, and almost all are suggested to go to b-school after their Research Associate stint. Good news is that they seem to be a feeder into HBS/GSB/Wharton. Bad news is there is no mobility up to the Analyst role. I know a few people there, and this seems to be the consensus.
• So D&C is definitely not the place to for FT out of undergrad if you're looking to stay long-term. If you're one of the very few who can get a long-term career at the shop, D&C is one of the best places to be -- it's just that the probability of being one of those people is very low. However, the exits to b-school and top value funds are pretty great. Past Research Associates have gone to Tiger Cubs (not Lone Pine, Viking, Tiger Global, but a step below), for example.

Now I can't speak as much to exits to L/S shops -- I think the reason is because the conservative, long-biased, longer-term time horizon mentality they have there isn't particularly conducive to the quicker styles of multimanager L/S shops. Of the list you provided, Shaw fundamental's strategy is the most similar. The rest are decidedly short-term shops.

Edit: you might also want to consider the FT hiring practices of these HFs. To my knowledge, Shaw fundamental and P72 Academy had no FT recruiting channels out of undergrad this year aside from SA (this was not the case in the past, but promotion is becoming increasingly internal). Citadel's Global Equities and Surveyor L/S platforms simply don't hire out of undergrad like their quant research and trading divisions do. Can't speak to BAM, but I imagine that they also source the majority of their FT hires from SA. If anything, if you wanted to move to these shops, you might be looking at 2 years down the line in the worst case scenario.