Personally, I'm not all too fond of L85's. I mean, yeah they're nice and all, but there's just something up with it that puts me off. I prefer the SA58, but the length and Mag difficulty are probably drawbacks.
In airsoft there's little to no reason to use an L85, all its real world advantages are of no value to an airsoft rifle, and they all use non-standard gearboxes too, so aside from the mags being harder to find I'd say the SA58 is better. No doubt easier to use too, the L85 is a pig to use in confined spaces, the bullpup config really limits the ways you can hold the rifle, makes it less pointable too, since you're holding it nearer the front.