Esc/Motor combos I've ran in the Muraco and the Shogun:
Max6: Hobbystar 4092, 4292, 4282, Kuron 825, Castle/Chastle (Chinese knockoff) 2200, TP4050 1570kv, 2100kv, Hobbystar 4274
MMX6S: Hobbystar 4282, Kuron 825, Castle/Chastle (Chinese knockoff) 2200, TP4050 1570kv, 2100kv, Hobbystar 4274
MMX8S: Kuron 825, Castle/Chastle (Chinese knockoff) 2200, TP4050 1570kv, 2100kv
Tekno ET48.3:
XR8 Pro (Gen 1)
XeRun G3 4274 2250KV
Both platforms have raced against a Losi 3.0 truggy and a ET48 2.0. The first promising combo for the Shogun was the MMX6 and Kuron motor. The current combo is a MMX6 and the HS 4274. She'll keep up with the Losi and the Tekno, but it takes a little more concentration to keep your lines clean. The Shogun is easily faster than the other two, but the straight is only one part of the track. In the infield, I have to pay much more attention to keep up with them. In the event that I am able to take a lead over the other two, I can hold it, but I cannot make mistakes in the infield or they will get on me quick. Changing the 52T spur out to a 46T seems to have calmed her down as well, making the infield a little easier to manage provided I pay attention to my speed coming into the corners.
The ET48.3 is definitely slower than the Shogun, but handles the infield so much better. I still need to concentrate, but not as much as I have to with the Shogun. The HW combo in the 48.3 has a smoother power delivery, which I think equates to smoother lines around the track. The 48.3 can easily pace the Losi and the 48 2.0; if I get a lead, it's usually easier for me to maintain and lengthen it. If I start behind, it's easier to catch up with the 48.3 than it is with the Shogun. Overtaking them is also easier with the 48.3.
My experience has been that while the Castle systems indeed seem to provide substantial punch, the HW system provides ample power for racing purposes. I have a feeling that if I play around with the Castle settings, I can get the power delivery to be on a similar wavelength to the HW. That should help make a better comparison of the two power plants. Also affecting the outcome is the weight of the Shogun; 9.34lbs. The 48.3 comes in at 8.26lbs. I'm sure geometry also plays a role, but at this level of racing, driver skill usually is the separating factor. I will venture to say that if you do install that combo, it'll make for a pretty good driving experience.
Just my 2 dollars worth.
EDIT:
Above was a response for CCB