I have a small garden front and back but have only been here since late summer.
Negatives:
- you don't get the light if you have high buildings around.
- we get mosquitoes, though reasonably close to the lake
- people can look in, though I discovered curtains
Positives:
- the garden is much bigger than a patio, space is increased outside tenfold
- light issue is compensated if you have a large window/patio door to the garden as it increases the amount of light you get
- our apartment feels a lot, lot larger with large patio windows at either end and then the garden bits
- our kid loves it and play with the neighbours' kids which is great for him
- we put one of those little plastic houses up for the boy, blimmin great fun. As was the paddling pool and a swing. Guess I would be less likely to do that in an apartment.
- we can run all the way round the apartment on the outside. Woohoo! Woot woot!
- Having lunch outside in the garden with plenty of space is great
- Never had to worry if my kids can climb over the balcony, just need to worry about them making a dash for it (though we are well off the road, also not in a very busy pass)
All in all, i'm in favour of
our garden apartment. We also have good neighbours so that helps.
I should add that I looked at 11 garden apartments before settling on this. I don't know if you have animals or children. We ruled some out because:
- location was busy. Too many people to look through your window, concern for children
- garden was not secure enough e.g. had a steep drop or was too near a road (saw some with fantastic views over lake Zurich, but price reflected it and really it was a roof garden)
- one garden apartment at a great place had a pool in the garden.

Might have been worried about the pool with small children, but expect we would have gotten over that... it was just not the right location / price etc
On a general note, prices tend to be a bit higher for garden apartments and of course by nature there are fewer of them. You have to check if you are going to share the garden or if it is all yours. Anyway hope that helps