In our area we service mostly summer homes. So installing outside saves you from having to track down the owners for access to controllers. Year round residence I usually install in Garage or utiliy rooms-Harry
Around here, people have come to expect them inside - on the wall in their garage. That's just the standard around here. 99% of the systems I see and install are like that.
I guess I prefer indoor controllers anyway. We use Rainbird ESP controllers, and the ESP Indoor controllers are quite a bit less $ than the outdoor controllers are. Second, there is almost never an outlet outside on most of the homes around here.
Most here are indoor. The manifold is rarely near an outlet to plug in, and the added cost of an outdoor timer and hard wiring could be the breaker in not getting a bid. Would prefer all outdoors, but not a big deal.
Worst one I've seen, between the floor joists in a crawl space with no light fixture to see what your doing.
Outdoors...all of them are outdoors hung at service panel. In Phoenix it never rains, freezes, hails, or anything else to cause problems and make us put them inside.
That being said...worse place I ever saw one was in the Master Bedroom. It was an extension cord plugged in outside and running through a tiny hole in the window...must have been drilled with a special diamond tip drill bit.....
The wierdest part was that it was an old Rainbird Mechanical timer....LOUD AS HELL....but they somehow learned to live with it.