I mean, I'm looking to buy a new theme because people have inspired me to build a cool looking base from theirs.
It really depends on what you're going for. The layouts are all the same, but the themes do differ enough to make some unique bases. I have one of each although I'm a terrible base decorator. I'll say this though, the Sewer and Ancient themes are the most unique ones in the sense that they have some animations that the rest do not. But anyway, think first of what your end product is and then pick a theme.
I'd suggest that you youtube-search each lair theme and have a look at what would suit you the best. There are videos out there showing every lair-theme available. I know that the Cave lair is a popular choice though, so is the Penthouse lair.
