I’d appreciate any thoughts on whether I should get a single large (450 volt/200 amp) Victron charge controller or several smaller VE.CAN charge controllers.
I’m leaning towards several smaller ones. I vaguely recall someone saying that the lower voltage charge controllers have better efficiency.
I've said this. It's important to point out that these efficiency differences are usually offset by wiring efficiencies, e.g., a 48V system with controller running at about 72Vmp is going to be at maximum conversion efficiency of about 1-2%; however, this may be gobbled up by wiring losses due to lower voltage and higher current. It's often a wash.
The higher voltage MPPT to attempt to minimize conversion inefficiencies in accordance with their anticipated operating voltages, and when one is looking at these higher voltages for longer wiring runs, they often present a notable overall improved efficiency due to reduced wiring losses.
Better efficiency combined with the greater reliability of multiple controllers would probably push me away from the big controller.
Revised for more appropriate context. That's really the only reason, particularly if your wiring runs are reasonable where a 150V controller would suffice.
There are a couple of massive advantages of the RS450 controllers.
1) multiple trackers: the 450/200 has four separate 450V/18A in trackers . Each tracker can output a maximum of 4000W with a combined maximum of 11,520W.
2) true galvanic isolation. While it's rare, even a Victron MPPT can fail and short panels to battery, which can be devastating. The RS450 line absolutely, positively can't short the panels to the battery.
The unit can also accept up to 20A Isc and retain reverse polarity protection. If you want to over-panel and are willing to forego reverse polarity protection, you can go to 30A Isc on each tracker.