While it's always possible to compare since they are both card games with creatures and spells, I think PvZ is a very different game and is targeted towards a different audience (though there are plenty of overlaps, of course). PvZ is meant to be for mobile gaming, it's meant to be fast (games are much faster) and more casual (different progression system) in the sense that people are meant to play a game here and there (the quest system encourages short burst of gaming).
For the intended purpose, I think it's very well designed and don't really see much point in comparing it to Hearthstone other than to clarify the differences.