Given your stats, it seems that you could probably go either way, as far as calories/nutrition go. Depending on the preparation of the burger, it may or may not offer you fewer calories than pizza. But again, given your stats, you probably don't need to worry that much either way.
So, it really depends on what you want to do AFTER your meal. Are you hoping to stay in the vicinity of the pizza friend's house? If your longer term plans are to hang out with that friend or to do some shopping/errands after eating, then I'd suggest going the pizza route.
On the other hand, you will probably have to chip in for the pizza,or depending on the stinginess of your friend, pay for all of it. A free ride on the burger may be totally worth it, depending on how much you want a burger relative to how much you want pizza.
However, if you're going for BigLaw, which you said you are, I think you'd almost have to go with the pizza. Firms like to see that you have friends and a life, versus mooching off your in-laws and eating dinner with parental figures. But I guess it really comes down to the money/location issues.