If your servers varka is full of bots, it will be better choosing ketra no matter what.
I do however find that soldier and captain badges are easier to kill at Varka than at Ketra (I'm 77 StS with 150 wind arcana and major arcana set, buffed by OL, SE and EE with PoWater). I collect badges on my boxed EE, so I can freely do both spots.
It feels like the equivalent badge on ketra always have more mdef than the varka mob.
As long as your meleeing you should be more than fine though.
you can always kill at ketras for your class transfer and then switch to varkas if you want to get your ally to a higher lvl (bosses are harder to get for ketras imo)..
With Gracia+ approaching, there is almost no reason to go to a high alliance level for Varka/Ketra. Just get to 79+ before Gracia Final, and make friends (or sub a good/useful class).
I am ally with Orcs, so I kill ketra and the reason I went that path is because most of my clannies were the same way and back in the days I did not know exactly the difference and I was told both were the same. So, I went with the flow and if I could go back in time I'll ally with Varka to kill orcs this time. Unfortunately, I am lvl 5 ally already and farmed couple of S recs and I am too lazy to start all over. I have not been in varka the last 2-3 months because bots.
Varka is full of bots in Devianne. Bots that stay 24x7 and stop only on Tuesdays when the server goes down for maintenance.
My priority today is to get my Alliance Lvl 2 to do the Class Change Quest, I'll ally myself with Varka Silenos I don't want to spend time by searching a spot.
After That I don't know, I don't really care of this quest I hate theses places for xp, and it s eems very long to get sthg :/