Ur lift not gonna break down everyday.

If high density then it will get annoying travelling up and down from the lift cause the higher your floor is, the more stops there would be to reach your destination.

Level 12 to Car park 6 would be a shorter distance than Level 21 to Cark Park 4.
Top floor exposes to the sun more and generally higher in temperature. If you on aircond 24/7 then no problem cause otherwise it will be much hotter compared to lower floor. It is actually a benefit for countries with 4 seasons because higher floor during winter will reduce heating cost but since Malaysia only has 1 season which is hot and humid everyday, then lower floor would be a better choice if you don't want to ramp up your aircond.

Bear in mind 12 floor is by no means "Lower Floor". It is normally a sweet spot I would say cause it is high enough to avoid all street noises and pests + a view that is wide enough but not too tall that you only see ants moving around while at the same time low enough to avoid too much heat and sunlight (especially when you live in building close to 30 floors (the 13-30 floors will shield you from the heat  )