I own a Subaru now, as well the F6B.

Both engines are "flat" engines, horizontally-opposed, one a four-banger, the six being in the Honda.

Both behave in similar ways...

-essentially no vibration at any engine speed...full throttle on the Subaru @ 6000 rpm is as smooth as 2000 rpm, same on the B
-simliar intake sound, particularly under heavy throttle inputs
-lower center of gravity contributes to flat, stable cornering
-both twist slightly when being cranked over by the starter motor
-both make a raspy, sporty sound during hard acceleration
-both make a unique exhaust note as compared to their inline counterparts

These flat motors have their downsides (spacing in certain applications, like motorcycle foot space; ease of some maintenance and repair items, increased costs due to having two banks of cylinders), but they have a lot of advantages that I never knew until I owned a couple of 'em.

In the Subaru, the flat-four is a short engine, located entirely in front of the wheels, allowing the transmission to be directly behind the PTO, with half-shafts coming out directly to the front wheels; a driveshaft heading out back to the rear. A lot less redundancy, and power loss, in this set up.