One of the biggest problems with jarred garlic is the fact that it is often wet, and in a preservative with a flavor that imparts to the food. Because it is not fresh, it will not have the same health benefits either.
This means in order to prepare it, you need to rinse it, dry it, before it is ready to go. Doing these things will mute the flavor even more for what is an already mute flavor compared to fresh garlic.
Given these issues, I would vastly prefer using the garlic tubes more commonly found in Europe, than I would a wet can or wet jarred garlic. Garlic tubes are fresh, preserve well, and in many cases have that pungent ajoene and allicin still present that give it a zing!
To add to this, I would prefer using a dried garlic spice over a can of jarred garlic if forced into deciding between the worst of most garlic options.