If only comparing Rey and Kylo, Rey is absolute garbge. Rey needs more non-faction toons to field her best offense and defense versions for GAC/TW/Arena. She is a bit higher of an investment (though I would argue this is largely irrelevant since in the grande scheme the investment is fairly minimal. The problem is that while at release they each seemed to have their area to shine, the way CG has handled balancing them post-release has left Rey significantly short. Depending on how exactly they approach the announced buff (that will stop 5s from working) it is likely that you will require JKR and GAS at high relic to be able to reliably climb against all SLKR variants. And for defense in GAC/TW you're probably gonna want L337 at a minimum, so assume you will need to relic them as well. Compared to SLKR who appears to only use Malak from outside their faction for arena and you've got a situation where one of your options basically has their whole team pulled from the toons needed to unlock vs Rey who requires multiple non-faction teams (and worse, leaders) available if you want to use her to reliably take down SLKR.
She's ridiculously OP in a vacuum, but is shit in the actual meta. If you go straight for her just plan on literally never winning a single round of GAC again. She will bloat your roster to hell and you don't have the GP to absorb that without it ruining your matchmaking. You will gain rey, your opponents will have relic'd GAS, Padme, and Sep Droids. You don't have the teams to reliably beat those 3 squads, so they will be able to block both their front zones while you will only be able to block 1 of yours. SLKR will at least let you have 2 good offense squads, (Hux and solo SLKR) and also will let you easily take 1st in heroic sith. And 1st in heroic sith is so, so much more gear than 10th.
The singular advantage Rey has is that she's usable in LSGeo while SLKR is not. But thanks to bugs she is not a guaranteed 4 waves completed, and even if she was the rewards for reliable t3 or 1st in Heroic Sith >>> the slight increase in rewards you may get from completing any extra waves in LSGeo. (and given your current roster, it'll be a long time before you can get into a guild that is doing LS)