Modulated Strip Miners II is the best miner available for barges and exhumers. While the base yield is lower than regular T1 Strip Miners, the bonuses you get from the crystals means that you are mining MUCH more than the T1 strips. I use T1 crystals, and usually carry 5-7 of each ore that I mine with me at any given time. To keep everything sorted neatly, I use a secure container that I have in my cargohold in order to store all my crystals. I use only T1 crystals because they are cheap to make, cheap to buy and last quite a while. T2 crystals can be up to 10 times as expensive, and last only a fraction of the time. Going off rough numbers here, but I believe T1 crystals will last an average of 200-300 cycles. T2 will last from 50-100 cycles. Personally, I dont see any point to using T2 crystals, since they cost a lot more and break much faster. I do not believe that the extra ISK invested in making/buying them is worth the extra yield percent bonus. But, that is something you will have to decide for yourselves.
My suggestion would to be to go ahead and train up for them, and use them for everything that you mine. The time invested is well worth the better miners, but DO NO USE THE T2 STRIP MINERS WITHOUT THE CRYSTALS!!!
Flow chart showing the different mining lasers in order from least yield to most yield:
Mining Laser I --> (Named) Mining Laser I --> Mining Laser II --> Modulated Strip Miner II (NO crystals) --> Strip Miner I --> Modulated Strip Miner II (WITH crystals)
By upgrading to the T2 strips and using crystals, you'll be investing in the best mining gear this game currently has to offer. Also, look into mining upgrades for your barges/exhumers, since they will add a good deal of ore that you can bring in per cycle.