What is the fastest SiC MOSFET?
The obvious first disclaimer is that you're using these devices in ways that they are not intended, YMMV. That being said, here is how you might compare devices. I think it will probably work well for non-linear amplifier types (class C, E, F), but linearity will be hard. Harmonics are also tricky as well - I've had hard-switching SiC MOSFET circuits with significant frequency components above 200 MHz.


The internal gate resistance on SiC MOSFETs is relatively high. Check this property on the datasheet. Some manufacturers have lower resistances. Using Ciss and Rgate, you can get a first order estimate of how much your input signal will be attenuated. 
The low output capacitance of SiC is only really an advantage if you're using them at significant fraction of their rated voltage. 
The TO-247-3 is the worst package for a SiC MOSFET. Look for 4-leaded TO-247 packages, or SMT footprints with a Kelvin source connection.
On the topic of packages, your layout is very important. The Crss of SiC MOSFETs is high, so if you aren't careful the device will turn itself on/off. This will look like oscillations on the switching edge. 
Ids max isn't the most useful metric for comparing, look at Coss times Rdson at your expected current and expected bus voltage.
SiC MOSFETs need to be driven all the way to the full specified Vgs to get the advertised Rdson, and they also don't really like negative Vgs. You might be seeing issues getting a large enough Vgs on the device turn it on hard. Since the limits on gate voltage are asymmetric, it can also be difficult to turn the device off.