I also use the Fox Predator net.
Upsides; It's big enough for decent doubles, fairly cheap (net only ?19.99), stiff and lightweight.
Downsides: It took me ages to find someone who had one in stock (Yately Angling Centre), it's a little awkward to carry (as are all round nets) and resting Barbel is a little more awkward than a triangular net. It's handy in fast flows and overgrown swims as it's not too deep and the mesh is just right. I've caught many treble hooks in the mesh when spinning for Perch and somehow, it's really easy to remove the hooks.
A mate has a Fox Barbel net (pole and net for under ?40). I'm always landing Barbel for him so I feel I'm in a decent position to relate an opinion.
Upsides; Plenty of room for the biggest Barbel, stiff (unlike many cheap tri nets I've used in the past), folds up and will stow easily in a rod sling (unlike a pan net) and is great for resting Barbel.
Downsides; I'd really like to be able to buy just the. I have loads of landing net poles already (including a Fox pole from a Carp net) and I don't want to pay for another have it sat at home collecting dust. I've emailed Fox to see if I can order just the net but have had no response. Come on Fox - get your finger out! Because of its' extra depth, it's a little unwieldy in fast flowing or overgrown swims.
I've never caught a Barbels' dorsal in either of the above nets, but that was very rare with my old cheap nets too.
I've seen Ron's net it's pretty damn good but I didn't like the brushed silver aluminium frame (too bright) or the expensive price tag.