I have been a member of WWB since 2009 and just recently joined SaleHoo. I never regretted my purchase of a WWB membership and feel that they do a really good job in several areas:
1. Helping you understand how to become a legal business
2. Teaching you how droshipping works
3. Teaching you how to work with wholesalers/dropship companies
4. Educating you on how to avoid getting scammed
5. Providing a solid directory of dropship and light bulk suppliers
6. Giving you a good understanding of how to build an ecommerce site
My chief complaint is with their market analysis tools which I feel need a major upgrade. Many new members accept their results as gospel but I find them to be unreliable and not worth using.
I've haven't had a chance to look through the Education and Research Labs on SaleHoo, so can't make a direct comparison between the two offerings. I have been impressed with what I've found here in terms of suppliers and believe it's easier to navigate and search on SaleHoo.
I feel like the combination of WWB and SaleHoo gives me a lot of flexibility for developing my niche retail stores. I tried Doba for a while but thought the monthly charge was way out of line for what they offered.
My gut says that if you are already a SaleHoo member, you probably don't need a WWB membership. I used WWB as my sole dropshipping source and launched multiple e-commerce sites succesfully, so they can be the foundation for an online business. There is quite a bit of overlap in suppliers between the two companies, but enough diversity that I am willing to pay for a yearly SaleHoo membership (WWB was a one-time $300 charge) to increase my options.
Despite a significant amount of bashing of WWB here, my experience was a good one. I do know that many people complained that there were not enough electronics dropshippers on WWB but I think this was a conscious decision. Profit margins on electronics are very thin and many of the suppliers I've seen here on SaleHoo look more like discounters than wholesale/dropshippers. I am always suspicous of companies that don't ask for a resale tax ID when setting up an account. Legitimate wholesalers require this.
For my online retail stores, I'd rather work with true wholesale companies that dropship and are selective about who they have selling their products.