sparring always gone through phases where certain devices or pings are dominant and that shapes everyone's stats
rough example of how I'd say things went in terms of ping
was almost no relevant delayers except maybe Ryo when I first started sparring in 2011 and the delay was manageable, that's when all the PCs came and were just freestomping iDevices with less experience - some iDevices did well but overall I don't think there was any reason a PC player should have been losing more than 30% to iDevices
that kept up for nearly 2 years, around the time that Mother won a few Mixed GSTs is when it slowly started to balance out and more higher-ping sparrers started winning a lot
2013 into 2014 is when people like Yui, Mood, Sarah, etc. were sparring quite a bit more - after that time is when I think sparring became more favorable for higher-ping players just due to the terrible server conditions because it creates an environment that they're used to sparring in
then 2016 was a lot of Sarah, Alexx, etc. - the low-ping sparrers that did spar did it because they were newer to the server and had some gas left in the tank (Brett, Brandon, etc.)
now it's just kind of whatever and even field for everyone because no one good even spars
just my opinion though, in terms of devices PCs have always had the upper hand (especially during US GST era) but most hardcore delayers are mobile players
TL;DR: ****ty server conditions and an influx of PCs in 2011 are mostly what have determined sparring stats over the years (obviously alongside natural factors like skill, etc.)