ok I will talk about the BBUK series, without any spoilers, so you can decide what's best for you...not gonna include BB3 and BB7 because I already told you.
BB5- One word. Flawless. Never gets boring.
BB8- First half is amazing, the girls in this series are the best ever. You may not like the male cast though...
BB9- Very diverse casting. Also a really good series, though most of the latecomers are boring (depends on who you ask again) and the final week, like most of the final weeks, is boring.
BB10- The tasks and the production were pretty bad this season tbh. Though the HMs really saved this series, and made it good, but not the BEST of the BEST tho.
BB11: Editing style is different, if you decide to watch the other series before this first. First half is good, but the second half just needed better HMs. The tasks were a step up from the previous year's tho.
Will continue tommorow, its like 2am where I live now...