“Which would you recommend?”
You're shopping for a laptop computer at a store. The salesperson has shown you two computers within your price range. You say this because you want to know which one he thinks is better.
Which would you recommend?
Use this phrase when you want to ask an expert to help you choose something. For example, at a restaurant you can ask the waiter to tell you what items are best by asking:
What would you recommend?
You usually use "which" when asking for the best out of 2 things, and "what" when asking about a larger group of choices.