I'm not comfortable blurring the lines between being an employee and a business owner. The mindset is different, for one. The only true benefit of that from my perspective is if you use a resume to obtain work and, as a VA, I don't provide a resume. I personally would rather NOT be considered an employee while trying to sell my services as a business.
This may be a good fit for some folks who are not comfortable with the concept of being a business owner and prefer to think of themselves as employees. However, you have to generate your own leads and business and you are basically paying for someone else to handle your paperwork. Yes, the health insurance is a benefit, but you are still paying the premiums. Again, you are primarily paying someone else to handle your paperwork.
The fee is 5% of your gross for both solow-2 and mbopartners, and you must generate a minimum of $5k/month income so their minimum monthly fee is $250/mth, for a minimum cost of $3,000/year and obviously increasing as your income does, as well. At my billing rate, I can still do my paperwork in less time per month than the $250 it would cost me for them to do it.
I truly don't see the benefits to me as a solo. Just my .02.