The benefits:
Fresh air: who woulda thought fresh air is really good for us. No need to expand on that.
Sunlight (hopefully) at any time of the day is incredible for us. So many health benefits but really we should all know that.
Earthing/grounding: either train bare foot or kick the shoes off after training for 20 mins. Again, incredible health benefits.
No artificial blue light: the less exposure we have to this, the better. Gyms are full of it so if you can, train outside.
No busy gyms or waiting for equipment: chances are you’re not gonna train on the high street and equipment will be yours so nice and quiet, alone time to just focus on you.
Opening times: no need to worry about opening times or busy periods as you can pick any time of any day to train.
The drawbacks:
Little to no equipment: depending on what you have, you could be lacking in toys and choices. If you wanna do a real heavy leg session for example, you may struggle.
No one to call help: chances are, you’ll be alone so if you do hurt yourself and need a spot, may be waiting a while.
Rain and wind: although training in the good weather is great, pouring down and wind are far less desirable conditions where one can easily make excuses to skip.
So benefits and drawbacks, most of these can be removed by having a gym membership so you can get the equipment you need on certain days and have a place to train when weather is bad.
For equipment and a spot outside, get a mobile coach who has toys that they bring.