So these guys seem to be in the same league

Both work best with blanks

spend a die vs reroll all

change one to guaranteed acc vs use all acc on the first roll(and second)

exhaust use vs exhaust use

5 points vs 5 points

so which is better? Go!

Depends on the role if your ship.

You might take leading shots instead and sensor teams for example.

Or Vader with sensor teams on GSDs

Of the two, my money is on Sensor Teams. Simply due to the current meta trending back towards ships without a Defensive Retrofit, Sensor Teams has a consistent effect on ships without Electronic Countermeasures.

Veteran Gunners, on the other hand, has limited usage in that it's only functional in an instance where you roll tremendously poor dice results, or when you need a hail mary roll to win or salvage a game. It is smarter to keep even slightly below average results than to reroll away good dice.

Each card has situations it wants to be in. Vet gunners tends to dislike large dice pools. Senor teams likes large pools but not too large that you would be better off brute forcing the acc. Interesting fineline of the two cards is Senor team likes Ackbar frigates while vet gunners like frigates at their normal firepower.

My take - if I am playing a large ship I usually wouldn't think I needed sensor teams as the large number of blue dice should generate reliable accuracy. Usually gunnery team + leading shots trumps both these options.

Liberty Star cruiser however seems to be a reasonable choice for Vet gunners because you can focus on the reds. You can add in SW7s I you really want.

Sensor teams for me is a lot more niche - you need a ship that is chucking a lot of dice but which has no other easy options for accuracy. My prime candidate in this case is a Glad 2. Possibly VSD 1.

I play with a number of people who just have back luck in rolls (one actually did a cr90 swarm with sw7s to garuntee damage) veteran gunners seems best for just back luck at rolling die

Veteran Gunners is really for big red dice pools, and/or medium sized ones with perhaps a smattering of black, that can't have TLRC. Vic 1s, MC30 Scouts, Glad 2, AFMk2 A; those are probably the only ships I would consider putting it on. Anything that can take Leading Shots would probably get that instead, though.

But even with those...eh...still don't love this upgrade. If it was 3 points (or less) it might be worth it. 5 is just too much. There are too many other things that compete for that slot better. In almost all the above examples I'd rather have ordnance experts for 1 point cheaper. MC30 scout probably wants ordnance experts and TLRC to handle it's belligerent dice, even though it costs more, unless you really want to do something else with your TL slot like x17.