With subs, bigger is almost always better than smaller if for no other reason than the cone doesn’t need to travel as far resulting in less distortion. It’s much easier to overload a 10” sub than it is a 12” sub and even if you only need a larger sub five percent of the time, then that will be five percent of the time you won’t be disappointed if you have the larger sub.
I to am a REL owner along with Rythmik and SVS and I agree with Hilde45 that Rythmik as well as SVS are a better deal. Though I will admit that REL has excellent customer service.