Keep in mind that you can rent many tools! Home Depot has a tool rental department, and then there are places like Sunbelt who do it as their main business.
If you are only going to need a tool for one job, you should probably rent it instead of buy. Also often if you rent a tool on a Friday you can keep it until Monday morning but only pay for one day of rental. That gives you all weekend to use it.
As far as air vs electric, air tools are less portable than electric ones. You need the air compressor and hoses wherever you are using it. Electricity is obviously easier to deal with.
An air chisel needs a lot of air. They come in different sizes, obviously. If you get a [email protected]
chisel and put it on a [email protected]
compressor, the compressor will work almost constantly to keep up with the tool. It might not last very long under that kind of duty-cycle.
Air tools also often need oil lubrication and some need low water content in the air to last a long time. So then you are looking at a water filter and oiler. Other kinds of tools (like paint sprayers) need the oil removed from the air!
So air tools can be kinda complicated. Unless you really think it is worth the investment in the compressor and don't mind buying the needed accessories to keep your tools working a long time, you might be better off with electric tools.