User blog comment:StarkBlack/Most Powerful Province?/@comment-25109952-20131016195539

To correctly answer this, we must look at landscape, location, size, defensibility and most importantly, resouces.

Landscape: High Rock is mountainous and surronded by water on three sides, Skyrim both mountainous and has forests. Morrowind is an ashland and Black Marsh a swamp. Cyrodiil is a perfect blend of all the different climates. Elsweyr has deserts and jungles, Valenwood is a massive jungle and Hammerfell a desert with some grass around it (Or maybe the other way around). I don't know what Summerset is like. High Rock being very mountainous and nearly completely surronded by water gives it the most defensible land.

Location: Cyrodiil is in the center and allows easy access to and from all provinces except High Rock and Summerset, making it the worst as invasion will be easier. High Rock's landscape and it's location away from Cyrodiil make it the hardest to invade. Summerset being an island is actually a very bad thing, as it can also be invaded from all sides. The only exception in Cyrodiil is the Imperial City, which is probably the Storm's End of Tamriel.

Size: Cyrodiil is the largest and I think the Summerset Isles are the smallest. Cyrodiil is therefore the worst, as troops would be spread thinner during an invasion.

Defensibility: Black Marsh is the obvious winner for obvious reasons. Though, without the Argonians any disease resistant/immune race (Bosmer) or anybody who knows a safe road through the damn province

Resources: Cyrodiil, obviously, is the heartland of Tamriel and most resources would be there. Solstheim belongs to Morrowind and it is rich in Ebony, giving it a massive advantage.

Overall, High Rock wins out in two of these, but Morrowind and Cyrodiil both have the best resources which equals the best army, but we are talking about the province, not the people themselves.

So, I believe High Rock would be the most powerful.