These two islands look almost identical and share the same design flaws, both maps being dominated by leviathans in the north.
Though similar in shape, there are actually significant differences between the two. FEI has far fewer regons overall, and a much higher proportion of cities. I believe the original idea was to allow for more, smaller realms. This used to be teh case. Shrinking player numbers have forced consolidation, though.
But I've heard there is some quality roleplay there and no shortage of war.
FEI is now in the middle of a war. It is the first war following the long road to re-establishing Arcaea as the Imperial giant on the island. There was a long period of peace following the defeat of Kindara and the establishment of the Imperium. Quite a few people thought the island would just wither away. Emperor Velax finally opened diplomacy up, and unlocked things, though. Sorraine and Coralynth immediately opened things up by pouncing on Ohnar West, but failing to achieve the quick kill. The result was that Sorraine and Coralynth got jumped on by Arcaea, Cathay, and the Principality of Zonasa, all claiming various reasons why they felt it necessary to join in the beat-down. A duchy split off of Arcaea, initially siding with the southerners in the war on Sorraine. Then that new realm (the Grand Duchy of the Dragon) tried to set itself up as the neutral buffer realm, between the north and south. The southerners said "Oh no you don't, that's OUR city!", changed their rationale for attacking Sorraine, and promptly violated the Grand Duchy's borders, and got their asses kicked in Colasan. (Again.)
Anyway, there's no shortage of war on FEI, it's just not a very exciting war. The southerners march forever, and tend to do a lot of sitting around between battles. Coralynth is small, and can't really do a lot. Ohnar West is small, and can't fight gainst Sorraine without Arcaea's help. Sorraine does a lot of fighting, but tends to be unorganized. Every time we try to make a move against OW, Arcaea moves in to stop it. Overall, it feels like there's a lot of going through the motions, but nothing really important happening.
On EC, there was a recent ruler change in Perdan, and a new realm formed by secesssion from Caligus, named Vix Tiramora. It is formed on land that used to belong to Perdan. Everyone was preparing for this secession to trigger a war involving most of the south. However, plans changed when Perdan's ruler changed. Perdan and Vix Tiramora are waging a staged war game, with each side wagering one region, with the war lasting 90 days. The rest of the island is scrambling to adapt to this, and looking for some other way to start some wars. How it all develops is not yet determined.
Which isle is actually more fun to play on? Maybe there are specific nations that are on the rise right now?
That all depends on how you define fun. At the moment, there is more war on FEI, but I don't really consider it to be a "fun" war. There's not a lot of war on EC right now (onlyPerdan/Vix), but there is a war brewing that could end up being very big. Or it might not happen at all. Dunno yet.