I like the flip helmets, thought they are noisier. It is nice to be able to open the face, either by the clear shield or the whole chin bar. The retractable dark sun shade is also handy. But whatever your preference, make sure that it is comfortable.
Sizes among manufacturers vary greatly, but within a brand hold pretty true, a small is a small and so on. Pay attention to the weight also. I have a Scorpion (XXL), and a HJC (small). Head fits well in both, but the HJC is about 5 ozs. lighter. About 1/3 lb. is a bunch of weight.
As far as the Sena products, The design of the base, clamp on unit. required that I make an incision in the LH cheek pad, along the outer welting. So that the clamp jaw could fit flush, without biting on a bunch of padding and apoulstery.
I have the 20s evo dual set. If you want to pair to you partner, the bike, and your phone. There is a bunch of stuff to remember. I am sure the 30 is similar.
The HJC has a cloth flap/pocket that covers the area where the speaker sets. This is good, it keeps your ear from rolling down as you slip the helmet on. You want the speakers against(touching) your ear. but not pressing on it. The kit comes with foam shims to get that fit right. I found it require me to "filet" one shim and attach velcro to the cut sides to get them just right.
Sena is good with their support, they will answer questions, and follow up to check if problems are solved.