Plants vs. Zombies is available for PC, iPad, and iPhone so far as I know. I'd like to help answer Plants vs. Zombies questions, but my knowledge is based on the PC version. So…
What platforms are Plants vs. Zombies available on?
Are there any major differences between the versions available on each platform such as: gameplay, campaign, puzzles, survival, achievements, or anything else?
Best Answer
Since you are already familiar with the PC version, I'll go into the other ones:
iPhone version
It contains the entire campaign, as well as different achievements (also different Easter eggs, such as what happen if you scroll down the achievement listing continuously). The puzzles are mainly the same as well.
iPad version
Identical to the iPhone version, except it now includes the Survival mode. However, now it includes a new way to improve the power of your cobb plants (by putting butter on enemies first). This is making use of the iPad multitouch mode of up to 11 touches at once (think launching multiple walnut in walnut bowling at once). Still no zen garden.
Read more on the Wiki here: Game versions of Plants vs. Zombies