According to the rules on spray attacks- it seems like what you have is a Weapon:6 attack that can spray just like an SMG... this shouldn't cost you anything extra since it doesn't cost the SMG anything extra.
But let's try both to see if it even matters anyway.
Assume your multiple attacks are handled by the spray attack rules (the only way to do it I know of in this system), meaning you roll accuracy once, and split any bonus up.
Let's also assume that you beat the target's defense by 3, and it has 4 stress boxes.
So, you could do
A) 9 stress in a single shot (weapon:6 + accuracy:3)
[take-out, or a mild+moderate consequence or major consequence]
B) 1, 1, 1, 2, 2, 2 (weapon:1 x3, weapon:1 + accuracy:1 x3), which will fill in boxes 1-6 in a single round
[take-out, or 2 mild consequences or mild+moderate (if no second mild avail)]
C) 1, 1, 1, 1, 1, 4 (weapon:1 x5, weapon:1 + accuracy:3), which will fill in boxes 1-6 in a single round
[take-out, or a mild+moderate consequence or a major consequence]
All 3 look pretty scary... all three are likely to result in a take-out or roughly the same consequences. B)'s pretty useless next to C)...
Against an unarmored target, I'd favor C) slightly, only because it guarantees that any future hits, no matter how small, result in a consequence or take-out.
Against even Armor:1, B) and C) become pretty useless pretty fast though, since it reduces all 6 hits by one damage each.
B) would only fill boxes 1-3, and C) would only fill box 3.
Seems pretty situational to me. Since flexibility is it's own kind of power, I'd say your GM would be within rights to set up a house-rule such that you have to buy that option on the EI (for a single point of it's bonus)... but until/unless he does, the RAW seems to support you getting to choose on the fly.
EDIT: admittedly, the question then becomes, do people think having split attack multi-tap a single target is ok at all? I'm not sure myself- it simultaneously seems reasonable from a simulationist's perspective... but from a gamer's perspective, it could easily end up ruining combat mechanics.