Mark is right. There would be no point of comparison between SaleHoo and AliExpress since both are operating differently. AliExpress is an e-Commerce website with sellers from China while SaleHoo is a directory of suppliers from all over the world including China. AliExpress is composed mostly of retailers selling by piece or "wholesale".
The BIG advantage of being a member of the SaleHoo community lies in the reliability of the listed suppliers. We all know China suppliers is infamous for generating customer complaints and with AliExpress having majority (if not, all) of their suppliers from mainland China then you would have some major sleuthing to do before you can guarantee the trustworthiness of the seller you want to be involved with. While SaleHoo's creed is to ensure verification of a supplier before even approving them to be a part of the directory. We even conduct timely check-ups on the supplier even to the point of doing sample orders just so our members need not to risk their money when dealing with our suppliers.
That being said, saving valuable research time, effort, and money are part of SaleHoo's checklist as a promise to our customers. Not to mention, the other offerings that Mark have mentioned! :)