Yes, depending on the brand you buy garlic capsules are stronger then eating a garlic bulb.
It's a large mis-understanding that all brands of the same herb have the same quality. That's how people who try herbs for the first time become negitive to herbs
when they end up buying a cheap brand that has no value.
As far a great book and very benefical, as well as helpful is "How To Be Your Own Herbal Pharmacist" By Linda Rector-Page
N.D., Ph.D.