Both Wholesale Suite and B2BKing are mature, capable products with tens of thousands of stores between them. The question is not whether they work — it is whether a small B2B store needs everything they carry.
The honest split
If you run a wholesale-only store — approved accounts, customer-specific pricing, quotes — buy the suite. If you sell to both retail and wholesale and mostly need minimum orders, multiples and quantity pricing, a focused plugin does that with a fraction of the setup.
We wrote the full side-by-side here: Quantity Manager vs. Wholesale Suite & B2BKing.
Info: Cost is not only the licence. A suite you spend a day configuring and then maintain across updates has a real time price too.