The Mac XL was a rebadged Lisa with MacWorks software installed to enable it to emulate the Mac. It also came with a small hardware kit to fix the screen aspect ratio, and therefore the Mac XL did have square pixels just like the Mac.
The biggest downside was the processor speed. The original Mac had an 8 MHz 68000, the Lisa was 6. Still it did have a larger screen and decent hard drives well before the Mac had these.
May 15, 1985: MacXL (Lisa) Officially Killed