I would go for Dell. I had both and Dell was more solid, had better usb placement etc. Also better GPU will give better graphics.
Still 4 GB ram is low AF, if its single port then consider pushing to 8GB version or even 16...
1 more thing:
check if its DDR4. This will make a LOT of difference.
https
/www.asus.com/pl/Laptops/ROG-Strix-GL503/specifications/
http/www.dell.com/pl/p/inspiron-15-7567-laptop/pd
both should be dual channel so you can add another ram stick later.
both have NVME so have potential for ultra fast SSD, on inspiron there might be problems with make it bootable.