Well, here's my question:
on Steam, there are Baldur's Gate Enhanced Edition and Baldur's Gate II Enhanced Edition. Each one sells for 20€ (yeah it's not exactly 20). Here there are Baldur's Gate and Baldur's Gate II, sold for less than 14$ if I buy the combo.
Do the GOG versions have the little add-ons the Steam versions have? Do they have enhanced graphics for large screens? I'm trying to decide if it's better to buy GOG's version today or Steam's version when it'll be on sale.
Thank you all for answering.

The Steam version of Baldur's Gate Enhanced Edition is filled up with some DRM and Baldur's Gate is a game many, many people end up playing over and over throughout their lives.

If you're that kind of person, I'd strongly recommend getting the GOG versions.

If you're more of a one-shot-and-done sort of person and you have your Internet connection and don't mind the DRM, then Steam is the better deal.

I personally have not played the Enhanced Editions yet. I might pick them up on a sale, but I think the old games play just fine. And I like the experience of stepping back in time and playing them like they played 15 years ago. I'll admit, though, the better GUI, wide-screen support and zoom looks nice.

I tried the mods for wide-screen with Baldur's Gate. It ruined the experience for me. It just didn't all go together very well. And your widescreen saves are not compatible with your 4:3 saves.

If you're not wanting to play them for a few months, GOG has offered a deal at least twice a year where you pay about $20 and you get Baldur's Gate 1 and 2 (the old originals), Neverwinter Nights 1+2, Icewind Dale 1+2, Temple of Elemental Evil (very good game, too), Planescape: Torment, DragonShard and Demon Stone (the latter are both skippable, but aren't horrible games). If you're not expecting to play them until around the summer, then I'd wait if you're on any kind of a gaming budget.

The Enhanced Editions also go on sale both at GOG and Steam usually two or three times a year. Steam's sale has been 50% off I believe. I can't remember GOG's discount.

Thank you both! I think I'll buy the Enhanced editions here then, because they cost much less then on Steam.