HP5+ is loved by many because of its ability to handle pushes. But Tri-X shouldn’t be ignored either, it’s a good film for that. This year, Tri-X dropped in price considerably, so it may be an economical option.
I haven’t pushed Ultramax previously. If you develop at a lab, it may be actually cheaper for you to get something like CineStill 800T and develop at box speed or push one stop (since labs often charge per stop pushed). I’ve had good luck pushing Pro Image 100 to 400 (which may be a similar experience to pushing Ultramax). However, it added a significant amount of contrast to the shadows, which is often the price you pay for pushing cheaper stocks. It could be worth a try anyway, depending on what you’re looking for.
If you’re planning to shoot dark scenes and are looking for clean results, you may be better off with B&W stocks as colour films may sometimes add colour noise to the shadows, which could be difficult to get rid of in post. Or you can just shoot Delta 3200 or T-Max P3200, which will be grainy but generally as good as you get at that ISO.
