EpicUK formation of 6 in the bt list for 350 is fun (shame its not in all the EpicUk lists).
A more full answer - pretend the Annihilator doesn't exist and compare the destructor with the vindicator
Speed 30cm, 4+, FF5+, CC6+, Autocannon, 2 heavy bolters
Speed 25cm, 4+, FF4+, CC6+, Demolisher
So same toughness. The Predator has a 10cm counter charge and a 5cm speed advantage. The Autocannon gives a limited shooting ability for 15cm more than the demolisher. In a FF a Vindie formation gets 2 hits, while a predator formation gets 1 1/3. The Vindicator has IC so no infantry cover saves.
Guns wise here they are for double, advance and sustain at 30cm.
4 Predator Destructor's (275 points)
Double
Not in cover 2AP / 1 1/3AP&1/3AT
In Cover 1AP / 2/3AP&2/9AT
Points per hit AP (in cover) 275
Advance
Not in cover 4AP / 2 2/3AP&2/3AT
In Cover 2AP / 1 1/3AP&1/3AT
Points per hit AP (in cover) 137.5
Sustain
Not in cover 6AP / 4AP&2AT
In Cover 4AP / 2 2/3AP&2/3AT
Points per hit AP (in cover) 68.75
4 Vindicators (250 points)
Double 2AP / 1 1/3AT
Points per hit AP 125
Advance 2 2/3AP / 2AT
Points per hit AP 93.75
Sustain 3 1/3AP / 2 2/3AT
Points per hit AP 75
Increase the vindie unit count to 6 for 350 and you get
Double 3AP / 2AT
Points per hit AP 116.67
Advance 4AP / 3AT
Points per hit AP 87.5
Sustain 5AP / 4AT
Points per hit AP 70
Remember IC further increases its ability to kill infantry as no horrible building saves, up to twice as good per hit than the predator then. The pred of course is better at killing things in the open and with greater speed might have a chance of catching things.
So against the destructor better firepower in everything but sustain (as long as the targets are in cover), slower, so more likely to be doubling, worse at responding to assaults, better at attacking in assaults and finally far better AT firepower if needs be, though at a shorter range.
4 compared to 4 the vindicator is I think a better air assault tank and all rounder, the predator thanks to its move a better tank deployed normally. Go to 6 strong and things get more even on the ground with little change in the air.
Add walker and its a closer choice on the ground and little change in the air. So probably walker and 350 for 6 would be on parity with the destructor on the ground

But its all moot as everyone normally takes predator annihilators if they run out of warhounds!
Give the damn things their thunderers back

Why is it not as fast? The Demolisher cannon and ammo puts a big strain on it and slows it down. Not seen as a problem in built up areas with its dozer blade and better armour however.
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