lets define what 3-gun you are referring to.
Are we discussing a build for 3 gun like we see in the states? (3 gun nation and events like that)
Or are we discussing tactical, room clearing, shoot from cover type of matches?
I only really shoot the first one.
I prefer the Benelli nova/supernova with a 24" barrel for Canada.
3.5" chamber means that the loading and ejection ports are larger than normal so loading is a little easier.
Comes with chokes.
Supernova comes with a comfortech stock which reduces recoil a little (or so they say)
If only shooting in Canada, I'd go with a pump for capacity.
If shooting US, you'll be more competitive with a semi and for that I would lean towards a Benelli M2.
I haven't handled or shot the Remington Versamax but it had been gaining popularity in 3gun circles in the US.