"Better" handling needs to be defined. If you want quick and nimble, shorter swingarm. If you want stable in high speed, you'll want a longer swingarm. Depending on the person, either can be "better".
And you can mix it up. Longer swingarm, but drop the forks up thru the trees a tad. And vice versa. Some racebikes have adjustble triple trees to change the rake/trail for different tracks. Some tracks have more slow speed turns, others are highspeed with banks.
When someone says "racing" to me, I think roadracing, and a longer SA is a choice, not always taken. Drag racing sure, keep the front wheel down.
If you are an interstate rider, you'll like the longer swingarm. If you go carving it up with the club on Sunday mornings, you'll prefer shorter, and drop the forks up the trees to keep up with the CBRs.
Better to take care of a headshake at the source and i'm sure HM has his opinion on that. Likely its a tire, rim, front wheel to rear wheel alignment issue. Assuming the steering head bearings are fresh. I think it should be cleared up without really changing anything like rake, trail, or swingarm length.
IMVHO