Marketon is a decent Mexican style grocery store. However, prices are quite a bit higher than La Bonita for basically the same exact type of stuff.
As an example, pico de gallo is $2.99 a pound at Marketon and at La Bonita it's only $1.99 per pound. The same thing applies to their marinated meat prices like diezmillo and ranchera (carne aside).
So, all the being said, they're not a bad option if they're close, but La Bonita has the same quality, same stuff and much better prices.