I can guarantee you that they're all pretty much the same. I've had ASRock, Gigabyte, Biostar, ECS/Elitegroup and MSi. Other than the fact that the MSi board failed on me, I've been 100% satisfied with their features and performance levels because motherboards have a very small (if any) effect on overall PC performance. As far as actual PC performance was concerned, I never noticed a difference between any brand because, let's face it, the actual working parts of the motherboards (the chipsets) are all supplied by AMD or Intel (although at the time, AMD chipsets were ATi and nVidia also had their nForce chipsets) so a board's features were dictated by which chipset was used. That's still true today.
When I worked at Tiger Direct, I had the opportunity to really look at the difference between many motherboard manufacturers because we had ASRock, ASUS, Biostar, ECS/Elitegroup, EVGA, Gigabyte, Jetway and XFX. The differences were mainly cosmetic with the biggest differences being the number of USB and SATA ports, the number of PCI and PCI-Express slots and whether or not they had IDE and Floppy Drive connectors. There weren't even huge differences when it came to the BIOS because they were all by American Megatrends.
I honestly don't know how ASUS got the reputation that it has because I've never found them to be overly-impressive. In fact, I've never been impressed enough to pay the extra cost associated with them and so I've never owned one. My stepfather, the one who got me into computers at the age of 8, has owned several ASUS motherboards but, like most Baby-Boomers, he's a bit of a brand-wh0re because, in his day, brand-names actually mattered so, you know, old habits and all that.
He got an ASUS TUF X570 motherboard and he had audio issues with it. He had to RMA it but he had no motherboard to use with his R9-3900X. I lent him my ASRock X370 Killer SLI board and then went back to install his TUF motherboard when he got it back many months later. He lives 3 hours away from me so I ended up driving 12 hours total. I bought him a Unicomp keyboard a couple of years prior (bloody expensive) and I found it, mostly unused, in his basement. He said it was too loud (well, it IS an IBM model M, so yeah...) and gave it to me (I love that thing!). In the end, he asked me if I just wanted to take his TUF board and leave the Killer SLI. I refused because I didn't think that trading an X570 board for an X370 board was fair to him and put the TUF back into his PC.
So, here's a guy who swears by ASUS but was satisfied with an ASRock X370 board to the point that he was willing to trade his ASUS TUF X570 for it. That should tell you all that you need to know about being a brand-wh0re when it comes to motherboards.