If you're buying an electronic ballast. It might take you about three years to save and recoup the price different from the electronic vs. tar ballast. IMHO, your electronic ballast might bite the dust b4 they even ge that old. Tar ballast tend to last longer. If the tar ballast do die out, you can usually replace the cap. with parts from Home Depot.
The reason I like electronic over cap and coil is that the electronic are more portable (take up less room) and run cooler. Of course, if you buy a big brand cap and coil ballast, it will come with a big heat sink to cool it down (vs. DIY.)
Look at all those live rocks on the beach at Florida's state park!