Here is a quick comparison for those interested since I owned both systems. I will add more as I come up with them.
M15x
Pros
Cons
G73
Pros
** This is no longer special to the Asus G73. The creator of Throttle stop has built this into his program.
Cons
Conclusion
In the end I prefer the M15x. *I wish I had the CPU OC capabilities of the G73 in the M15x but that is the only thing I will miss. Upgrade-ability, better cooling and better build quality is more important to me. I also had a lot of issues with Asus customer support, that is not an experience I want to go through again. So for now I sold my G73 and will run with my M15x and **M17x until there is a new toy out there to play with.
Update
*This is no longer true thanks to throttlestop. The M15x is a better performer all around with less issues.
**Big FAIL returned this also. Maybe I will try it again once the 480M is released.
M15x
Pros
- Great build quality. No anodized aluminum like the M17x but it feels really sturdy and looks good.
- Nice LED LCD. It's no RGB LED but as far as LED screens go it's very nice, not washed out like some LED screens I've seen.
- Easy to upgrade. The GPU, CPU, Hard Drive, Memory and CMOS battery are all accessible by removing the bottom cover which means removing the system battery and two screws. It's as eay as your average barebone system.
- Standard MXM 3.0 slot. I was able to upgrade my nvidia 240M to an ATI 5870 that can be bought for Clevo systems. I was even able to use the MSI vbios on the card to activate ATI Overdrive through CCC.
Pics of the ATI 5870 in the M15x.
- Separate fan and heatsink for the GPU and CPU. This type of setup is normally reserved for 17" systems.
- No chiclet keyboard which is a big plus for me....I hate the new trend of going to chiclet keyboards.
- AlienFX which now interacts with games like Dark Void....very cool.
Cons
- Might as well be a 17" system with one hard drive....it's as heavy as one.
- Dell does not offer the system with the ATI 5870 only the ATI 5850. You need to do the upgrade yourself if you want it.
- No CPU OC capabilities in the BIOS for the 920XM.
- Huge LCD bezel makes it look funny.
G73
Pros
- Best CPU OC'ing capabilities for a laptop. Not only is the TDP and TDC settings in the BIOS unlocked when using a 920XM**, setfsb works with this system AND Asus has it's own twin-turbo software which increases the CPU frequency from 133Mhz to 142Mhz.
- Nice 17" 1920-x1080 LED LCD. Again one of the better non-RGB LED screens I've seen.
- Light-weight for a 17" system.
- ATI 5870 comes standard with this system along with 8GB of memory.
** This is no longer special to the Asus G73. The creator of Throttle stop has built this into his program.
Cons
- Build quality is sub-par. I once bought a $300 MSI barebone just to use and abuse. The build quality felt cheap and flimsy...The G73 reminded me of that cheap build quality. The first one I had didn't even sit flush on my desk.
- Non-standard GPU. Don't try changing the GPU in this system, Asus built this on it's own PCB board that is over-sized and would never fit in any other system. If you try to add the Clevo ATI card to it the screws won't line up and the heatsink won't sit flush.
- Not an easy upgrade. To get to the GPU and CPU you need to completely disassemble the system and remove the system board. This makes something as simple as replacing thermal paste a long and drawn out task.
- GPU runs too hot in this system. Idles about 10C higher than the M15x and when gaming if it get's too out you may get the dreaded GSOD.
- Keyboard lag issues. Apparently this is a common problem with Asus laptops. It has something to do with the way the ribbon cable is manufactured.
Conclusion
In the end I prefer the M15x. *I wish I had the CPU OC capabilities of the G73 in the M15x but that is the only thing I will miss. Upgrade-ability, better cooling and better build quality is more important to me. I also had a lot of issues with Asus customer support, that is not an experience I want to go through again. So for now I sold my G73 and will run with my M15x and **M17x until there is a new toy out there to play with.
Update
*This is no longer true thanks to throttlestop. The M15x is a better performer all around with less issues.
**Big FAIL returned this also. Maybe I will try it again once the 480M is released.
I just ordered the M15X last weekend and can't wait for it's arrival. 
