Weapon Loadout on Defender Mk3

Hey guys, so I recently upgraded my defender to mk3.
As mk2, I used to run Cannon + Sniper Cannon.
But now with 3 total points, I can have 1 1-point weapon and 1 2-point weapon.
I'm thinking of keeping the cannon, but what about for the other weapon slot?
I've been debating on these 3 options so far:
1) Tritorp -> I like this since i can just send these out as secondary option with cannon as primary weapon
2) Railgun -> i like this because i can sit back and do damage from far away
3) Explosive Cannon -> i am often close up with enemy, might as well shoot them for high damage too

Which one would be the best for Defender Mk3?