There are two Hiltons in Budapest -- we stayed at the Castle Hilton, and it was fantastic! However, as a Diamond, we got all the perks, so that may temper your conclusions somewhat.

What I had heard before I made the res:

1. The Castle location was really great for tourist stuff (and the lounge, treatment, etc were all great - true).

2. The West End Hilton is fine for more business-oriented activities, being on the Pest side and closer to all the stuff over there.

3. The Marriott has killer views and a very good lounge. Plus, great treatment for Golds and Silvers.

Since you have no status with either Marriott or Hilton, and assuming you want to do the tourist stuff, I'd lean a little toward the Castle Hilton, but you also can't go wrong with the Marriott.

Not much help, I know, but at least I can assure you you won't be disappointed with either.

It's a great city -- you'll enjoy it!