MY ACTUAL MONOSHOCK EXPERIENCE...
"Is one rear suspension method better than the other? Or is it simply a cost issue?"
After a long riding layoff, several years ago I bought a little '01 Honda VLX "starter" cruiser, with 583cc, and, unfortunately, toyota sedan performance.
We have WORLD CLASS rotten roads in my community, and I was assured by the Honda dealer that the monoshock was the functional equivalent of the standard external two rear shock setup. With a bad back, believe me, it was a question I asked several times.
The answer to the question, based on my experience, is NO!; a single monoshockwill not provide the same amount of suspenson function as traditional external twin rear shocks!
And then I found out that mother Honda had , starting with the '99 model. "improved". i.e.-changed, the rear setup, including swingarm and rear mono shock, on the bike I already have.
What the above change meant is that NO ONE yet makes a replacement aftermarket monoshock upgrade for this recently improved model! And I called ALL the suspension companies, too; several times~
I traded the bike after a year of poor functioning monoshock butt and back torture!
And, ya know, since Honda OWNS Showa, I can't figure out why MOST Honda buyers wind up having to upgrade their suspensions, regardless of type! Honda, (Performancce First!), should equip ALL their bikes with a great functioning Showa shock right off the boat!