Hi Philim,
They're quite different to each other - the Radiance have a lot of character and are quite mid-forward, the 305's are more laid back with a drier "meatier" sound. I'd say neither was "better" than the other but would more depend on personal taste.
I had a local chap pop in a couple of months back after he'd seen the Radiance 2's win a group test but as he was closer to us than a dealer we arranged to let him have a listen. He wasn't that keen on Radiance 2's for his taste of big band / swing music (too much emphasis on the horns) so we went through most of our ranges and the 305's were by far his favourite. He felt the 301's were very good and a close second but on a slower Sinatra track ("It Was a Very Good Year", from memory) they couldn't quite convey the deep richness of his voice as well as the floorstander.
If you have a system which lacks a little life then I'd say the Radiance would help inject a little spark into it, if you wanted a more balanced sound then I'd go with the 3-Series.