My choice is "old".

That said, switch back and forth on every scene and see what they've done with it in the new graphics style.

The old graphics still look great in my opinion, although I do have some serious nostalgia for these games for what it's worth. I still have no idea how people were able to cram that much detail into such low resolutions back then, still boggles my mind.

I really didn't like the update Guybrush model in the first remaster, so I played with old graphics plus voice acting. I thought they did a much better job in the second one, so I played that with the new graphics (and I would constantly stop to listen to the director's commentary which was a great addition).

I prefer the old graphics. The new ones are fine, but it doesn't have the same charm for whatever reason. It's probably just nostalgia, but I do like pixel art so it could have something to do with that, too. I don't know.

It's easy to switch back and forth, so you can mix and match if you like. I played with new but almost every time I visited a new place I would take a look around in the old graphics style. You might even find you want to play through it a second time anyway (it's quite short when you know where to go, after all). They're both pretty good-looking IMO, I think my slight preference for new might be in part because I didn't play it on original release - we'll see how I feel about this topic when Day of the Tentacle comes out (which I do have a ton of childhood nostalgia for the original look of).

As I recall, the first game did not let you keep the voice acting when you switched to the old graphics, which is kind of the main reason to play the special edition IMO. Barring that I'd consider switching to the old more often.

I switch back and forth, i love how fluid it is. Tickles me endlessly. Plus, it can be a nice way for me to try ferreting out details i missed. A change of perspective can do wonders. (I never played the game back in the day, so it's all new to me)