The Mora triflex is a good knife. I found that it was the easiest of the Moras that I own to clean up the bevels. It took me about 30 minutes using my inexpensive knife sharpening gear to get a good smooth edge on it. The triflex costs less than the similar knife with the Sandvik blade.
I own the 511 and the 546. It seems to me that the stainless is a little more difficult to sharpen. The metal does not seem to come off as fast. Perhaps the edge will be a little tougher and less prone to chipping.
For the price, both knives are a good deal. If the price for the Bushcraft Stainless was the same as the Bushcraft Triflex I would have gotten the stainless. Even if you keep your carbon knife stored in a dry location you should take it out and oil it once a year.