well, according to at least one person, the mac doesn't have very good agriculture apps.
there is no doubt that the mac platform has less apps available. and there are lots of little apps that only run on windows that we sometimes wish we had. i think your hobby example is a good one. when looking for apps to aid in landscaping, i found plenty for windows, a few for mac os 9 and only a couple of pitiful ones for os x.
on the other hand, almost every possible type of application the average person would normally use has an os x version or equivilent. and more are constantly being developed. the exception to this is games. while we have some good games, if that would be 50% or more of the time you spend computing, the mac is a poor choice.
just don't expect the lightening speed of the latest pc's. the memory management of os x that provides for greater stability, often takes a second or 2 off of some tasks. get there quick and crash on a pc or take a bit longer and know you won't have to reboot if anything were to go wrong, are your choices here.
it will also take you awhile to realize that most things aren't so complicated to do on a mac, once you've switched. but don't be under the illusion that everything always works perfectly on a mac. we have shoddy developers and hardware companies that don't know what they are doing just like wintels do.