I'm a relative newbie but it seems to me that 9's are the new standard for the modern guitarist.
PRSes came strung with .009s for many years. At some point in the mid-'00s they began stringing them with .010s at the factory.
I'm not sure there's a new 'modern guitarist' standard, but if there is, it surely isn't .009 ga. strings - they've been around for more than 50 years!
I played .009 'Super Slinkys' in the late '60s, and so did millions of other players, including lots of famous ones, like Jimmy Page. Yeah, the late '60s feel as long ago to me as they sound to you!
Despite my own history with .009s, I switched to .010s around 2000.
I wanted more precision in my playing. .009s feel like rubber bands in my hands compared to .010s. I found that the lighter strings bent so easily when fretted, they were more likely go sharp, especially with arpeggios and rhythm parts. And I have a very light touch! Once I got used to .010s, I couldn't go back. I do recording for a living, I can't have notes go off pitch.
Around that time, I also switched to smaller, heavier gauge picks to increase accuracy; As with strings, I don't want my pick flopping around when it comes off a string, I want it ready for the next note. I also feel I have more subtle control when I hold the pick closer to the point.
Personal preference, of course, this is NOT a prescription for other players. And I'm not saying players who like .009s should switch, nor am I saying .010s are somehow 'better'. Just explaining why I chose them.
Incidentally, my son, who's a pretty modern guy and also makes his livelihood in music and audio, plays .010s as well. So much for new standards!