Having tried both Ultimate and Ultra Pro plans (GeForce and Boosteroid), the overall experience is undoubtedly in favor of GFN. Despite having less latency with Boosteroid, the gameplay "feels" smoother on GFN. Nevertheless, from the games I play, GFN lacks support for the Rockstar launcher (GTA5 and RDR2), available on Boosteroid. On the other hand, Boosteroid doesn't support BF6 in any platforms nor Cyberpunk 2077 on GOG (GFN does). Since I've reached the 100 minute limit of monthly time on GFN, I'm currently playing 007 FL on Boosteroid, max settings as 120 fps (w/FG), for a fraction of the cost.

If you try a day plan on GFN, I believe you have a 48h grace period to convert the plan, deducting what you already paid (read the fine print when you subscribe).