2nd con- Most of the time the ground units are much smaller and host building equipment like washer and dryers.
The pro is that they are more affordable
2nd pro- No stairs to hassle with.
3rd- stays much cooler in the summer
walking up and down the stairs with your groceries, garbage, dry cleaning or whatever you must carry at the moment but NOT hearing the footsteps above your head all the time. Ground level you have an easier time without the stairs but will hear the people above. In a walk up I prefer the top floor but it varies per building.
Garden units will flood first too.
Now, if its an elevator building its obviously about the view and natural light. Usually you get better of both on a higher floor which is why the price increases as you go up. I like the higher floors in both personally.
Top Floors offer the advantage of no one living above you, so you do not hear people walking above you. It also tends to be more secure, but don't fool yourself, they might get broken into as well. You will generally have a better view and maybe have a rooftop deck, though sometimes that is common space and all units can use it but you would be closer. The negative is carrying groceries up and climbing all those stairs (but you might save on your health club costs!). If you have an elevator then it is less of an issue.
First floor has the benefit of easy access for you. you may also get some patio or yard space. You may not have anyone living below you (though sometimes there is a garden unit) so you might not have to worry about someone complaining about you walking across your floor. Depending on the type of building and the access points to your unit the first floor may be less secure.
So, the big issue is what will fit your lifestyle better?