After cleared out the first island (as a mage), I can say AP IS harder than TL. While early on you could already hire kickass units like inquisitors, archmages or even black knights, I don't know if there's some mechanism changed or there are simply fewer weak encouters but more harder encounters this time, but I'm facing many problems this early on:
1. Mana is a BIG concern this time, 80% of the fights I end up with not enough mana to manuever the battle. You simply can't pwn everything with fireballs, because enemy armies are BIG and it's harder to increase attributes this time.
2. Money is a BIG concern this time too, I'm completely broke down to a couple hundreds of gold now. Maybe it's because expensive units are earlier for hire now.
3. Encounters are simply harder now. It's really difficult to find a "equal strength" mob and you must face tougher armies if you want to make progress.
Other things which aren't about difficulties but still worth to mention:
1. Level up mechanism changed this time: each time you level up you're awarded with much more runes, and skills like Higher Magic take much less runes to learn too, so you'll be able to learn all the skills at the basic level very fast. Also, this time, when you level up it seems you don't get to choose what attritube you can improve, you just simply increase your leadership, which may explain why mana is strongly strained early on.
2. All troops are more unique now because they've tons of special abilities added in. Even guardsmen have some stupidly annoying 30% evasion (when they've lost over 70% of number). All in all units are very fun to choose and use.
3. Most of the skills have been revamped. Many of the skills like holy avenger seems so overpowered but actually fits the increased difficulty nicely. And perhaps it's to help offset the fact you can't choose to improve attritubes or rage/mana pool at levelling ups, many skills now have the effect of increasing attritubes or rage/mana pool.
4. New units, unit skills and spells are quite cool. Demonologists rocks, the Executioners (uber-demons) they can summon is even more so. Assassins are annoying. And the pirates can fucking evade attacks. The new Guardian Angel spells seem very powerful too, dealing ridiculous damage to anything attacking the warded troop.
5. The little dragon. All I can say is, it is VERY useful, even if you just spam the starting skill. And this time, even playing as a mage, I ALWAYS have sufficient rage to let it do something. Treasure Searcher seems pretty amazing, it'll give use extra chests of runes or money to dig up. And money is scarce this time. Did I mention its starting skill is VERY useful? Try it and you'll understand.
6. Why must my fucking princess all have the same look, just with different hair colour and costume? I want a long haired mysterious chick not some tomboy in bikini armor.
I'm pretty satisfied with the game so far, though at times it gets pretty depressing when I've found the weakest mob I can face is at least "slightly stronger". No I'm no pussy!