EvilLoynis: Here's the thing, that 3 picks not only starts you on Myrror with that +5 mana but it also allows you to pick 1 of 5 "Elite" type races that you cannot otherwise choose.
That's true, but it's still a lot to give up when you can ultimately get Paladins with High Men.
FWIW, Beastmen do nothing for me. The Minotaurs are good, but also unbearably slow. Dark Elves are good, but the crushing growth penalty makes them tricky. Draconians are fun, and flying units is a powerful ability, but I find their high-level units (Air Ships) disappointing. They're effective, but stylistically lacking. Dwarves are very, very good. Their bonuses are really powerful (if you have a city of them next to a couple of gold squares, you'll be rolling in money) and their engineers are by far the best. Hammerhands are nice, although the Golems are a bit disappointing.
You're underrating Trolls, IMO. They're superb at what they do best, which is a rush strategy. Their regular units are powerful enough to wipe the floor with the units of other races in the early game, plus they have regeneration. True, their building options are limited and they can't use mithril or adamantium, but if you use them right that's a strength not a weakness. Troll cities won't be wasting time building stuff they don't need, and you don't have to waste time searching for special metals for optimum city sites.
Besides, War Trolls are the second-best unit in the game after Paladins, IMO. Especially with Black Channels or - less awesome but still good - Chaos Channels.
To get back to the point, though, the Myrran races are fun, but they all have liabilities that make them tougher to play than most of the normal races. Three picks at start is a high price to pay to start on Myrror. It
is worth it if you are alone there, but probably not if you have to compete with one or more rivals. That's the big reason to stat on Myrror, to avoid having to fight for territory until you get your kingdom rolling.
Also, you don't have to pick one of the Myrran races if you pick Myrran at startup. You can start on Myrror and still take High Men, for example. It can be quite effective, particularly if you take a race like Barbarians, because all the Myrran races are slow-growth. You can overwhelm them with your population advantage.