Personally, I have been using a mixbox for most of MK11's life. MixBoxs are sort of invented specifically for Tekken by the Tekken community. I ran a HitBox in MKx and IJ2, but I came to disliked the base design philosophy of the HitBox. As a big guy (I'm 6'5) the tiny buttons annoy me but the real issue was that my brain just can't get to grips with that thumb button jump thing, splitting the movement over two hands.
What I love about the MixBox is that it has "proper", standard arcade buttons sizes and layouts, while still retaining that neat "HitBox" style input. This made transitioning from Arcade Stick, which used to be my main input device, a lot easier. The downside of course is that it is that "w,a,s,d" thing. I mean it is very cool, but I would prefer normal buttons.
There is a new MixBox making round at the moment called PXN X8... it is a budget controller coming in at 60usd. If you are interested in trying the controller then this would be a good option. It is a cheap one, like it dose not use proper Sanwa buttons... but it is "apparently" pretty good if you want to try out the idea of this controller and not spend the 400 for the pro-level MixBox Arcade.
There are a lot of strange, super high quality hitBox type things out now, like the Enth NE-KRCK. Still these actually enhance what I dislike about the HitBox. My brain is old.. I ain't making new neural pathways easy. I don't want to "play the controller" like a piano with all my fingers doing crazy independent thing. I like ...one had input, one hand buttons and basic default game layouts (or slightly tweaked in NRS's case) These super fance hitboxs are just not my thing.
Let's not forget that Diago's custom hitbox for SFIV was banned by Capcom.. so learning one of these is a big question mark if you plan to attend events.
If I was technically able I would build my own HitBox using the standard 8 arcade buttons on the right and then use nice smaller HitBox style buttons to make the "w,a,s,d" area. Sort of combining the two worlds.