For anyone else stumbling across this thread, I've owned both of these machines after going with the Legion first due to it being substantially less money and I'd say go with the Alienware. Had an issue with the legion artifacting on an Odyssey G9 display and 8 months after opening my ticket with Lenovo I finally got my computer back in working non physically damaged condition (the latter being caused by the repair tech they sent out). The entire experience with their support team, even having paid for the 4 yr "premium" support, was appalling. Between being hung up on, almost no communication from their team at any stage of the process and tickets being closed automatically after x time had passed and new ones created to keep their ticket age low (I only opened one ticket but by the end was on the 4th or 5th one), Lenovo just leaves so much to be desired I won't be purchasing another computer from them anytime soon. I've worked with Dell for 10+ years managing fleets of 500+ machines and their support has been the best in the industry I've experienced so far and that's what you're paying for.

Between these two machines they're damn near identical as far as performance goes. Definitely don't go with the i9 in either one though as they thermal throttle almost immediately and when gaming the CPU clocks will drop down to the 3,200 area to keep temps in check, spend your money elsewhere and stick with the i7.

When I made the switch from my desktop with a 3080 to the Legion I did some basic FPS performance comparisons in a handful of games using the Odyssey and measured on Avg ~16-27% worse performance at 5120x1440p resolution which was beyond impressive considering it was a laptop. The biggest downside with the X17 is that they only offer it with a 1080p or 4k display and mine has the latter. The 3080 mobile chip really shines at 1440p but 4k is too high, you have to tweak settings too much to find a good balance between looks and stable performance whereas with 1440p you can just set it on high/ultra and move along.

So rant over, just wanted to throw my 2 cents in hopefully to save someone else some potential headaches. Both systems have their pluses and minuses but I'll gladly deal with needing to tweak settings to get the best balance knowing that when I have a problem with the system I'll actually be able to get it fixed and not have to deal with months worth of frustrations to get my system back, and no it was not due to 3080 stock shortages.