All classes get 25% more hp and SP if they rebirth first. This is a BIG DEAL for both RK and RG, as both are tanking characters with skills that directly depend on max or current hp.
You also need the skills from trans to be useful:
RK:
Spear Dynamo - Spammable endure, and a very large hit bonus in one skill.
Clashing Spiral - Godly leveling skill well into third job.
Frenzy - Good to have.
Aura Blade, Parrying, good if you want to end up as a sword build.
RG:
Rapid smiting - this actually does good damage now.
Gloria Domini is a Good Skill.
Some people like getting BC as well.
Moreover, Crusader/Paladin need every skill point they can get. The second job skill tree for sader/pally forces you to make hard choices about where to put your skills. The skill tree for knight/LK on the other hand only has you make easy choices.
There are no cons to transing first, nor pros to non-trans, other than that they're faster to make - but leveling below level 99 isn't hard anymore, most of the time is in 100-150, not 1-99-1-99.
Edited by DrAzzy, 02 May 2011 - 04:11 PM.