Last time I checked, the Supreme amps were solid state equivalents of the Ultra/XXX/JSX amps. They even went as far as to have a transformer coupled push pull power section with Global Negative feedback so the topology is about 90% to that of a tube amp, just with the tubes replaced with solid state transistors. To top it off the transtube technology was Peavey's clever design to make a solid state discrete circuit that acts like preamp tubes, AMT Electronics has somethign similar with their solid state tubes, which is a rather old technology from back in the 60s as a way fro silicon to slowly phase out vacuum tubes. It wasn't until recently when the tonal characteristics of preamp tubes were fully realized and redeveloped.
For that alone, I would say go for the Peavey, it will have the tube topology and contain most of the tube quirk. The Randal I believe is simply a mosfet design, while better and tends to operate in similar fashion to tubes, its still not the same. One problem with the Supreme I think, it may have been the XL is that it is a transformer coupled power amp, meaning that even though it is solid state, it still has to be plugged into a load at all times. For the most part the supply voltage and winding ratio of the transformer should be high enough to do damage or as much damage, it is still something you have to watch out for.