In 2015 when I went to Hungary I only visited one of the baths, on my second trip I went to both Budapest Baths, the Széchenyi Thermal Bath and the the Gellért Thermal Bath. Take a look at my thoughts on both! The first, and arguably the more famous, is which has a much larger outdoor complex and may just be famous for being yellow (similar to another yellow structure in that part of the world). It is open every day from 6am to 10pm so the hours should not be the reason you can’t squeeze in a visit. Highly recommended to bring your own swimsuit, towel, and slippers / flip flops as you can rent them but they are quite pricey.
If you want a cabana, a small wooden room the size of an outhouse, it will cost you 6,200 FT ($21 USD) though I recommend going with a daily ticket with a locker for 5,7000 ($19) especially as your admission bracelet also serves as your key for the locker. Then you have free reign of the 13 indoor pools, ranging from 28C to 40C (82 to 104), and then 3 massive outdoor pools. You can find more information here.
The second, Gellért Thermal Bath is located on the Buda side of the city (the less touristy, more residential side) and the baths are part of the larger Hotel Gellert Complex. If you are heading to the baths from Pest like we were you can cross the beautiful green Liberty Bridge and get a great view of the complex as you approach, crossing the Danube River on your way.
Admission tickets to the Gellért Thermal Bath , which are advisable to book ahead of time online, vary in price based on the day of week but give you access to all of the pools – indoor and outdoor – for the remainder of the day. Compared to Széchenyi, the tile work in the indoor pools is definitely more intricate and beautiful as are the skylights and stained glass but the outdoor pools pale in comparison. They each have their advantages! We also opted fort the Royal Thermal massage (the price varies on time of day and length of massage) which was good but definitely not as much pressure as Western standards.
Would you want to go to the Budapest Baths?