YOU feel comfortable with. No matter what you are told here it is only going to be someone's opinion because BEST is relative.
Since a complete reading of your post appears to indicate that you want someone to say "get the Mac" because you had a good experience using your girlfriend's then go for it.
I have always been pretty faithful to PCs I always have enjoyed the many options you have when you decide to upgrade your laptop.
I understand windows inside and out, I have always loved it. I was a PC tech at Circuit City for years and am Microsoft Certified.
In the recent years I have gotten big into attempting to make music (via DAW / Production software) and DJing. (at least two times a week at a bar / wedding etc.) I have always had a great experience with most of the production software until recently. I have been having issues with audio pops and crackles. After hours of extensive research I have found that many users are having the same issues with PC based laptops with specs more than capable of running these programs. (Ableton, Maschine, Traktor, FL Studio) I have traced it to a single problem thanks to a programs called LatencyMon. It seems that some of the best PCs specs wise can be brought down with a single driver. It seems many PCs have the one required drivers to run (updated to newest version) that seems to cause latency in the audio processing. I did more research and found this is because programers cannot set a actual absolute runtime on their executions on Windows programs because it it not a "Real Time Operating System" (meaning that the values of run times and latencies are not set in stone and can cause your machine to hang causing little audio drop outs)
I have even found a reference of a guy running DPC latency checker on all the current laptops at best buy (i know its best buy but come on a ton of those have 2.4GHZ + i7 laptops) and only two barely performing with little DPC latency and even the occasionally spike occurred. When your Djings these DPC latencies cause crackling or even stop the program your are using. I cannot cannot have this! It shut down on me once live and I hate this. Why is it that all windows PCs laptops seems to always have DPC latencies?
I feel like my only options for reliability is MAC! Every other DJ i know uses one. Also I had to use my girlfriends Macbook Pro (2.6ghz i7 + 8gb ram) and it worked outside at a festival (Fun Fun Fun Fest in Austin, TX super dusty, and hot!) for 3 days 10 hours a day! It really opened my first professional experience with a MacI It did not stutter or hiccup once! I have always been a windows fan boy! I know its not windows fault, they just make the software. Unfortunately we have to rely on the people who make the laptops to make awesome drivers.... thats not always the case. It seems like since mac has a limited hardware sets up that the hardware support is more focused on limited hardware so they have maybe.. spent more time on it? I know the specs will be way better if i spend the same amount on a PC, but is that pc going to use the specs correctly? I assume its like a motor and a transmission. Intel being the Car (since the mac the processors) and OSX or Windows being the transmission. You can have the fastest engine in the world but if the transmission cannot properly displace the power... would you not agree that it is smart to buy the car that be the fastest if you thats what you need? Also the car that seems to never break down..
MAIN QUESTION: Do I have to buy a MacBook Pro in order to really feel and know im safe at my DJ gigs? I really wanted a Asus N56 (the one with the upgraded i7 3840qm off of x-otic) but I am afraid that unfortunately windows will not be reliable enough.) Even if Windows is stable enough can I count on the hardware manufacturers to provide latency free drivers for Windows?
.... ever since that 3 day dust fest + hot weather the i7 mac has proved its ability to professionally get the job done. I had no worries of it going out by the second day, it was a great feeling! plus The unibody aluminum design seemed to keep the dust out perfectly. It seems a lot of windows PC have a exposed fan, that would maybe even suck up all that bad dust?
It seems like 90% of the problems on my DJ softwares forums are from windows PCs, some really nice ones too!
I'm calling out to all the nerds who know about DPC Latencies and what a Real Time Operatin System!
P.S. I've had a lot of wine so I might be all over the place with my post but let me know if you have any questions to get my point