Coming from someone who has been involved with MIDI from the day it all started back around the mid 80's the two oldest programs that still have the best feature set and simplistic approach to MIDI and MIDI editing are Cubase and Cakewalk (which is now called Sonar). Cubase was developed by Steinberg in Germany, and Cakewalk was developed by 12 Tone Systems in the US.
These programs were all developed using actual musicians for musicians to produce songs using MIDI equipment. Over the years many other companies have entered the market and developed some tools that allow a non musician to have a hand in creating music that the computer could generate using processes that automatically create a musical phrase. These phrases can then be compiled into a song that a person can utilise as a complete composition. Most of these products create a song that is highly recognised as Elevator or Weather Channel music. It is very repetitive and always uses sounds that are very sterile and lifeless.
This method has allowed the developers to get a larger market share in the way of sales but has not contributed much to the musician because the tools needed to create a song are mostly in the hands of a skilled musician and not a novice hobbyist.
There have been a few new developers that have entered the marketplace but on a more serious level such as Pro-Tools and Nuendo but at a much higher cost due to them using proprietary hardware. This software has married MIDI & AUDIO in one common objective and that is to utilise all the methods of creating & recording sound into one solution.
Most of the computer related music has been generated using an IBM PC when MIDI was first released and Apple started a bit later but with only one program which started on the PC platform but later moved to Apple which is called Logic. Around 1993 Pro-Tools was a company that was originally designed to record audio on an Apple platform added MIDI to it's software for expanded capabilities of the new samplers that were also entering the production marketplace. MIDI was staring to find it's way into big film production by artists such as Hans Zimmer whereby the entire film was synchronised using MIDI to trigger all the sound effects and music simultaneously.
A more recent player has come on to the Apple side called Garage Band which has also employed MIDI to access the various Virtual Instruments that come standard with Garage Band.
As you can see there are a lot of programs that utilise MIDI to create music but each person must sort through where their priorities are and buy accordingly. It is also important to stay with your purchase so you can become proficient with your software. If you keep trying different software expecting it to be easier to use then you will never learn to be proficient with any of the packages out there.
Lastly, it matters not what platform you are on as the end results are all the same be it a PC or an Apple computer.