I won't bother adding or detracting from what everyone's already said. I will say though that going bigger adds a lot more personal stress. Obviously it costs more to build bigger; bigger motors, bigger ESCs, bigger cameras, bigger gimbals but it's also a lot more stressful to fly. Not more difficult per se, just more stressful. There's the fear of breaking stuff that cost you a lot when you crash obviously, but there also the added responsibility of flying a much heavier, bulkier machine around. It's just nowhere near as relaxed as flying a much smaller quadcopter. I'm kind of forced into flying bigger stuff because people I work with keep demanding it, but I do see a future where smaller is better, a not too distant future at that.
Anyway, that's all a bit philosophical. I would say just get the Cinestar if you can afford it and you feel that's what you want. It's not a stupid investment. If you build it yourself and decide you don't like it, you could probably get your money back by selling it ready to fly if you change your mind afterwards.