I'm looking at putting in a 5kw system to take advantage of the FL rebate program. I like the idea of running 2 identical arrays with the GT3.0 so you can cross check any failures. Also, the system would run at lower capacity and have expandability. The GT5.0 is about $700 cheaper and a little bit more efficient.

Do you think there is any real world benefit to dual GT3.0s, or should I just get the cheaper GT5?

Dual has a little more complex wiring (2 of them vs 1) will need 4 blank spaces in breaker panel.

Dual is more flexible, if not all panels face the same direction, it could help balance and not have mis-matched panels.

I personally like the extra redundancy idea, leave enough wire in the pull box so you can actually play with things, if need be.

I don't think there would/should be any "odd" interaction between them, but if there is - let us know.

I've run dual GT3.X for about 2.5 years, now a single GT5.0 for about 4 months, personally, I like the Single unit. Only one unit to monitor, its runs more efficient as its in the sweet spot long and the unit is CEC rated about 1% better and if a lightning hit takes out the unit, its one vs two to replace.

Either way you will be happy, GT5.0 is a simpler install.