Raw edge is a design for more side grip. Ariens does not specify anything special in either belt so not needed. Just say you were experiencing slip you would look for an issue unrelated to needing a raw edge belt. If you get a raw edge to correct slip you’d be correcting the wrong way.
Kevlar is just a better fabric, stronger cords and backing
A regular belt would be fine (you got a bunch of years of regular belts). A straight Kevlar belt would also be fine. I read that raw edge belts tend to send out more of the black fluff than regular belts which is not good in the tractor area where there's grease and oil for it to stick to.
If ordering online go with a site that gives the right Ariens dimensions although you can’t always count on that. Most replacements for 37.88 will be 38 and 34.50 a 35 so not really OEM.
If going to an auto place you get an outdoor power equipment belt not an auto belt. A hardware place will usually only have OPE belts and most Kevlar (blue or green). You can adjust the tensioners for and differences.
For a no issue replacement get Ariens belts.
07219100 1 V Belt 4L-Section 37.88 x .56
07210700 1 V-Belt 3L-Section 34.50 x .406
