Are SiC Mosfets better than Si Mosfets for Solar Charger in max 550V Range
My question is: Are SiC Mosfets an appropriate technology to
incorporate into &lt;=550V power switching? Will I gain power conversion
efficiencies with them compared to other more standard Si Fets in that
power range? Or, do those efficiencies deteriorate at lower voltages
-- where Si Mosfets would do just as well?

Comparing two devices in the links (Si = FCP125N65S3 and the Cree C3M0120065K), they both have about the same on resistance, max voltage and max current. However, the MOSFET will be slightly more efficient at around 50 kHz but, at speeds probably in excess of 200 kHz the SiC will probably be better due to its lower gate-source capacitance.
The Cree (SiC) will require a more sophisticated protection regime to avoid thermal runaway compared to the regular Si device because most SiCs don't avoid this even in switching applications. Si MOSFETs do avoid this problem rather well.
The gate drive voltages for SiC are about 150% higher than regular Si too. This both causes losses and slows things down a little bit and, designing a SiC gate driver needs a little more thought compared to Si. However, there's still a good chance that SiC will be significantly faster than Si and should be operated at a higher speed.
If the bulk diode is at all utilized for any form of flyback management then the SiC will be better because it has a faster reverse recovery time of 15 ns compared to 339 ns for the silicon but, the diode power losses are far more significant in the SiC compared to the Si.
Remember, this is a quick data sheet-to-data sheet side by side comparison. A true comparison only ever happens when you compare a circuit against another circuit because some parameters will be more important than others.