I also have a 425 AWS and love it. Don't know how it might be different than a new 7-iron, but I'm getting ready to start on season 16 with my deck. Other than dirt and some paint wear, it looks and cuts greats. No repairs. I'm even on the original belt, which still looks good too. And, I've put mine through pretty rough usage every year. I only get 2 seaons out of a set of blades. Then they are so beat up that it's hard to sharpen and balance them without grinding for a long time. I would think the "standard" deck on an X700 series would still be one heck of a good deck. Should last for many many years.
The AWS is great on slopes, around trees, plowing snow, etc. Almost as fast at cutting as a zero turn. Excellent traction and stability. Here is the issue with AWS: can't add a loader. Not sure if it's still the case with the new x700s, but on mine you can't add wheel weights because the rims are inside out. You have to use suitcase weights, which I actually like. Also, to put chains on mine, you have buy spacers so that the chains clear the AWS mechanisms. Not a big deal, and actually gives you a wider stance.
Having used one now for 15 years, I can't see not using AWS on my property. If mine ever fails, I'll be looking for another to replace it. I'd love to have an X700. But, too expensive new. Maybe by the time I'm ready I can find a used one for "cheap".
*If I were the OP, I'd be looking for a nice used 425 or 455 AWS and keep the $8000 in my pocket.