There are endless debates about the advantages and disadvantages of PC and Mac platforms. Both work well, have stable operating systems, plethora of recording studio software packages and both are used in professional studios. The answer to the question "Which is better?" is meaningless. Both can be used in recording studio.
First you should check if the software application that you want to use runs only on Mac or PC, or on both? If it only runs on one platform, either PC or Mac, then the decision about which platform to choose has been made for you already - you must get that computer to run your software.
Existing studio equipment - do you already have some computer in your recording studio? On what platform does your existing recording studio software run? Do you have only PCs, only Macs or both? If you have both platforms then you already know them well and you don't have a dilemma. But if you have only one platform then it is best to stick with it. It will be much easier to connect computers to a local network and to transfer projects and music files between computers.
The next criteria is your experience. Have you already worked with Windows or Mac OS? If you already have experience with Windows it makes sense to go for PC/Windows platform unless you have a very good reason to switch to Mac platform.
If the software runs on both platforms, then you should check whether the feature sets are identical on both platforms, or not. Usually the software is developed primarily for one platform and was later ported to other platforms. This means that the feature set leads on native platform and lags on other platforms. A typical example was Pro Tools which was primarily developed on the Mac and PC was closely behind. Digidesign claims that they aim to achieve parity between Mac and PC versions as soon as possible. It seems that today there is no significant difference between Mac and PC versions.
If performance is extremely important to you then you also need to find out which computer is technically more capable. Don't just compare processor frequency or some other number as this can be misleading. The best way to compare two computers is to actually run your target software and do some performance tests. The same applies to laptops, there can be huge differences between different models.
Price is another consideration. Go for the fastest computer you can afford with as much RAM as possible. Very soon your computer will be showing signs of age, and after a couple of years you will definitely want to buy a new faster computer again. In general, the fastest computers, by definition, are the more expensive models, but there are exceptions. Before you buy you should check compatibility with your hardware (and also with software). Some cheaper computers might have some compatibility or driver issues. It is always a good idea to check audio software/hardware requirements before you start selecting computer. Remember, you will not buy a computer because it is cheap, you will buy it to run you software reliably without problems. So price should not be your main criteria!
Ease of use and, more to the point, ease of finding and fixing problems are two other major and important considerations. Years ago Macs used to be easier to use than the PCs. Not anymore. Windows Vista or the older Windows XP are user friendly and stable operating systems used in many professional environments. When it comes to faultfinding and troubleshooting, the Mac is maybe a little easier to cope with than the PC. But onece you solve your problem you also get some experience and later it is much easier. You alrready know where to look for and wat to check. Both platforms have excellent support on the web so finding solution for your problem should be quite easy.
With either Mac or PC, you will be able to run professional recording studio software of your choice. Just make sure you look for compatibility and performance first, and only then compare prices.