Well the slave out for mesas is derived from the speaker jack, so is a line signal post power amp..
So either tube or solid should work and sound just fine.. I Haven't tried it through a stand alone solid state amp, but you should be able to preserve the tube tone with no problems.. It'll be the cheaper option..
Tube amp... can't go wrong with a tube amp.. Perhaps look into a 2:90 or 2:50 if you want a tube slave.. Or buy another Mesa or other brand secondhand for the power amp.
Have heard some people slave straight into a mixer.. I've tried that once or twice but the mixers I've used never liked it much..
If the 410 you have is just a speaker cab, the MarkV 90W definitely has enough grunt to drive two cabs without using a slave.. You'll have to push it a little more but it will work..
(On its own, I run my dual rect through a 4x12 and a 2x12.. Just fine)
if the two cabs are different impedance you may have a difference in volume between them..
If the 410 is a combo amp, you could slave one of the amps into the other easily enough.. But that means sacrificing one of the preamps..unless you can split each cab into a stereo cab, then each amp would have its output speaker load and then with the use of a tube stereo power amp, you could slave the amps and use the remaining speakers all without having to have another cabinet..
My situation is a little different.. I have a dual rec.. And a fender hotrod deluxe..
The cleans on the recto aren't that spectacular.. The cleans on the fender are great..
The dirty on the Mesa is awesome, the dirty on the fender isn't..
Mesa is 100W, fender is 40W... not much unity there..
But... My dual rect has a parallel effects loop, so.. I have the preamp of the fender going into the effects return on the Mesa for more headroom.. The parallel loop still allows me full use of the Mesa channels too.. But I don't want to lose the use of the open speaker on the combo or waste the power amp of the fender.. So I'm slaving my dual rec with my fenders power amp.
The open back of the fender lets the clean of the Mesa open up a bit.. And tames the bass from the other channels..
And the ability to combine the cleans from both amps really complement each other... Other combinations of channels don't sound great..
And Given the fender is a single speaker combo there's no major risk of blowing the speaker by slaving vs just using the speaker as a cab extension.. (Which the Mesa would chew up and spit out)
The extra tube power amp adds a little more compression and it sounds great with the combination of a 2x12 and the open back fender combo.. And the slave out does offer in effect an extra volume control..
now I have the Chimey fender cleans punching through the 100W power amp of the Mesa and good dirty sounds from the Mesa itself..
Takes a bit to balance but works a treat..
Who would have thought there would actually be an upside to a parallel effect loop..