High-quality music can be recorded on either a PC or a Mac. Most software (including the industry-leading Pro Tools) can be used on either platform; however, each type of computer has its pluses and minuses.
Apple computers come from the factory with Garageband, a fairly powerful music recording program. This fact alone makes Macs a good choice for learning how to make and record music via computer. The higher-end Mac that you buy, the better you will be able to make music.
Most PCs do not come with any multitrack recording programs, so you will have to purchase production software from a third party. While lower-end PCs may have difficulty running high-end recording programs, higher-end PCs will have no problems whatsoever.
Most professional recording studios use Macs to record music. This is, in part, due to the fact that Macs have fewer viruses and tend to crash less than PCs. Macs, however, generally cost more than PCs, so if cost is an issue, stick with a PC (if price is a concern, free downloadable music recording software is available). Whatever computer you choose, make sure it can run whatever music production software you plan to use.