i can't help you w/differences - go to revox's website, & find their local distributor. i think the usa distributor is in tennessee...
i *do* know that the b261 is an outstanding tuna - excellent sonics, great sensitivity, *and* selectivity. not quite as warm as my fave onix bwd1 w/soap power supply, it may be favored in a different system, or by someone w/different tastes. even tho it's digital, it can be detuned, say, to 98.3125, instead of 98.3, if, for example, there's a too-strong adjacent station at 98.1.
i have a b760 that functions much the same as the b261; it's supposed to be even better sonically, but i haven't tried it yet...
doug s.