Sorylians can dominate in Frigates and Cruiser squadrons. Their Frigates are some of thebest in the game, and having 4-strong cruiser squadrons makes grown opponents cry. Also, I love their gunships. Aside from the carrier though, their Tier-1's are a little blah. I'm a BIG fan of the Hasta Battlecruisers though - perhaps my favorite battlecruiser in the game.
Lastly, Sorylians favor broadsides for their main shots, so if you like oblique approaches and crossing the "T", they're for you.
Dindrenzi are more straightforward, literally. All fixed forward main guns. No Shields, but higher DR/CR with ablative armor. Weak vs SRS tokens. Brutal in every other way. Very strong Tier-1 ships! They rely on mines if foes get behind, or better, a squadron of rare Gunships.
In Planetfall, I like both.