I got my first sabers in last week, one has a single color 12w+ indigo LED and the other has the RGBA option. The single color is brighter for sure, but the other one doesn't look dull beside it by any means, even though I primarily have that saber set to pure red, which will always look more dull to the human eye than something in the green or blue range. I think if you're only going to have one saber for a while, or you want the best of all worlds with a ton of options, RGBA is the way to go as the small sacrifice to brightness is, well... Small.
That's just my 2 cents, I haven't been into this hobby for very long. As I said, these are my first, but since I have them in hand and can compare side to side I think that counts for something. You can see them both in my avatar and while the indigo looks way brighter to the camera, they're a lot closer looking in person.