I think the 306 is worth trying, for sure. To me, it falls somewhere between the 510 and the 901 - it feels very balanced.
I like LR 510's, but I've always found they make the flavor just a little bit acidic, if that makes sense. I get less of that with the 306 - the flavor seems better.
The 306 is a smaller atty, and therefore doesn't hold quite as much juice. I also find them a bit more fiddly to get on and off, because they are exposed, and if the metal gets a bit wet from juice, the drip tip will start to spin around it rather than screwing/unscrewing it, and you have to pinch on it a bit to get it off.
But, I think it's worth it for how they vape. I use both LR 510's and LR 306's, and I like both, but they are a little different.
Hey, it's worth a shot. It'll thread on all your 510 stuff, and it's not *extremely* different, so if you like the 510, you'll probably like the 306.
At absolute worst, you have a compatible back-up atty. At best, you may find a new favorite vape.