gaul is best def tribe in the game or you think you can be just as effective as teuton?
Yes gaul is without question the best overall defense tribe but it doesn't mean defense teuton doesn't work. Like I said there is nothing wrong with spearfighter, it's the best cavalry defender in the game and has the cheapest total defense as well (though phalanx isn't far behind and their stats are divided in what is arguably more useful way). The real nice feature of the teuton defense is the active playstyle with raider paladin forces which other nations can't easily replicate. You really just need a team to back your spears up or raid to justify paladins.
Should also be said that teuton is arguably best defense choice for a king or duke becausee of the wall being the best in the game which is very valuable to dukes and kings as fights will happen in treasuries much more often than in any other village type.