Absolutely. The most important reason of all is that there is a larger player base. Which additionally means there is a marketplace both in game and on the Exchange Market to buy/sell items.
The drawback that most people on Isen whine about, is that on Jainus, there are upgrade weapons that you are unable to purchase anymore unless you buy from another player. These weapons are pretty powerful, but they are not quite as game breaking as they once were. If you want to obtain one they usually cost somewhere between 20k-50k e-cash for most weapons except Katar 3.0 and Xbow 3.0, which are considerably more.
If you use an Opaniel or Abyss weapon (readily available and plentiful in supply) you'll be able to do well enough to farm in Mirror dungeons or Abyss maps and kill players as well if thats your thing. If you accept that you probably won't be able to obtain an upgrade weapon for a while until you've farmed some e-cash then you'll be fine.
One thing about coming back to Rohan is that at some point someone is gonna make you their bitch and rpk you. That'll happen on both servers and as far as I can see, you'll have more fun on Jainus.