I have the smallHD DP7 OLED and I would definitely recommend the HighBright for daylight viewable. What I found helpful was to use the matte screen cover. I much prefer matte over glossy any day of the week. I still can absolutely see focus. I also have a 7" marshall HDMI only. obviously this is not ideal for steadicam, but I have always loved the Marshall monitors.
I will say that I have had quite a few problems with my smallHD. Out of nowhere, the main board just fried. It wasnt abused, it was well packed, i had just finished 10 days with it. And then it just wouldnt turn on. $750 and 10 days later it is now back to normal. I also have the AB mount on it. While this is very helpful, I have, on two or three occasions, had a battery "overload" while powering only the monitor, which resulted in the monitor shutting off. This could very well be a battery issue, but I just want to note it.
Neither the smallHD nor the Marshall have ever been my steadicam monitor on my current rig. I have a Transvideo eSBL for that.
My old Archer 2 used a marshall 7" and it was terrific, but on 2 or 3 separate occasions I had ACs fry the board by switching from 12v to 24v on the rig. I am not sure about the flyer's electronics, but just be careful !!
If it is only going to be a sled monitor and not for use by an AC or DP...I think I would put my cash on a Marshall by a hair. Simply because it has never failed me. It also has fewer bells and whistles and things that can go wrong. I also am not a fan of touchscreen (smallHD) but that is not a deal maker. Tiffen also seems to put Marshalls on their rigs, so they may have some pre-existing cabling for you.
have a good one!