Malteurop is a multinational conglomerate based in France. They have malting plants and offices through the US, Canada and Europe.
Briess is a family owned malting company based in Chilton, WI.
That may explain the difference in price.
The best way to compare the two malts is to know the variety of barley used, the specifics of the malting process used and the weather conditions the barley was grown under. Sometimes a malt analysis sheet will contain this information, other times you simply have to call the maltster and ask.
Variety of Barley - affects the plumpness of the kernel, the protein content, and other malting conditions like sprout time etc...
Weather Conditions - obviously drought or wetter than normal conditions will adversely affect the barley (not as many plump kernels or more mold/fungus)
Malting process - generally well controlled by batch to account for variances in the kernels
Statements of the type, 'I like this malt or that malt better than the other malt' are just blanket statements with no real basis. You may have gotten lucky and received a batch of plumper than normal kernels from one malster where the other maltster for that particular batch was using barley grown during a drought which may have just passed their standards.
Then there's the political end of things, do you really want to support Ultra-Mega Corp? Or do you want to give your money to a family owned business. The choice is yours.