Rogue- Rogues start with two daggers, dual-wielded.
- Rogues start with +1 CON.
- Rogues start with the Pawn Talent.
- Rogues start with Dual Wielding and Sneak. (I recommend changing Sneak to Thievery.)
- Rogues start out with Throwing Knife and Adrenaline
Shadowblade- Shadowblades start with one dagger.
- Shadowblades start with +2 WIT.
- Shadowblades start with Guerrilla. (It is BAD. Change that immediately!)
- Shadowblades start with Polymorph and Thievery (Thievery is better as the first Civil skill.)
- Shadowblades start out with Chameleon Cloak and Chicken Claw.
Both of them start with +2 FIN, Scoundrel, and Backlash.
Either way, you should probably change something. Sneak is not that useful, and if you really want both, you can be a (living) Dwarf Rogue. The Guerrilla Talent on Shadowblade is very bad and pretty much no one should take it. The Pawn is better.
I honestly don't really see much advantage to starting out as a Shadowblade. You get fewer daggers and no weapon skill, which means less damage, which means that it'll be harder to chip away at enemy armor to make use of Chicken Claw.
If you want Polymorph, you can start as a Rogue and spec into that before you ever really need Invisibility, and missing out on Adrenaline would be a mistake. (Throwing Knife you can take or leave.)
