I find Forbes wax is great when applied to the clay body (quick drying, resists well and water-based so it cleans up easily). However, Forbes has a tendency to peel when applied to certain glazes.
Here's a blog link with a some good info about Forbes and Mobilcer resists.
Here's what Highwater says about these waxes:
Note: Mobilcer is oil-based and Forbes is water-based.
Forbes wax is a water-based wax that is good for waxing the bottoms of pots. It dries quickly and can only be used on top of glazes that contain gums and binders. It will not stick to dusty glaze surfaces for resist decoration. This is the wax Linda Arbuckle uses for her stunning majolica pots.
Mobil wax is oil-based and thicker than Forbes. Mobile works well for wax resist glaze decoration and takes about 30 minutes to dry. Even though it is oil-based, Mobile can be thinned with water to improve brushability. If it separates during storage, shake well before use.
Do not allow either wax to freeze.