It depends entirely on what you like.
I have both, an old AirHead BMW and an old Ironhead Sportster.
Logically the BM is the better bike.
But the Harley gets ridden more, lots more, including some long haul touring.
The BM is an efficient appliance. The Harley is just a hoot.
The Harley is easier to fix than the BM - and the Harley requires lots less special tools and knowledge, specially in the BM transmission/bevel areas.
The Harley has been more reliable than the BM - probably because I did a full rebuild on the Harley before riding it whereas I just fix things as they wear out/break on the BM (ie contantly).
Also Harley parts are waaay cheaper than BM parts.
Ideally, keep your BM and buy the Harley too. Then you have the best of both worlds.
'77 Harley Ironhead 6,000 miles across Oz
Reryder (AKA Hopper)
1977 Harley Sportster
01 HONDA VFR800
Ancient Harley 45, Snortster (Sporty engine in a Norton), Norton Atlas, Honda 350/4, Ariel HS scrambler