Y&B club lounges have the exact same offerings. We are the same resort. Same cast members, same managers. The sizes are pretty much the same since the BC was enlarged.
What is more important for you, full balcony or view? Personally I'd go with the deluxe room at the BC but you are correct that you could get a patio or a standing balcony. But the views are nice in those rooms. If you are going for a full balcony and that is the most important thing for you, I'd go with the YC. However, the "garden" views on club level on both sides are really "standard" views and in my opinion (and remember, this is must my opinion), both have fifty percent pretty ugly standard views and you have an equal chance at both the YC and BC to get those ugly views. At the BC standard view club levels, about 95% of them have full balconies so you would most likely get a full balcony there too.
There is absolutely no way you can guarantee to get a nice view and a full balcony at either resort by booking a standard view or deluxe view club level. The only way you can guarantee a full balcony and a nice view is to book the water view club level at the Yacht Club.
If it were me, hands down, absolutely with no hesitation, I'd go with the deluxe room at the Beach Club but that's me - that way I would be guaranteed a larger room and a nice view. I'm sure you can ask the next five people on this thread and they will most likely pick something different.