DRG probably has the most dry and straightforward rotation, much like a BLM, with a slight emphasis on positionals.

Then there's the weaving in of Jumps between GCDs.

SAM is just about building Sen and maintaining buffs and let off your most powerful attacks, weaving kenki skills between combos.

Overall, DRG doesn't have as much burst potential as SAM, but once you get the DRG rotation down, you can get pretty consistent DPS.

Then again, DRG also have more 'ranged' skills than SAM and 3 gap closers...

And the final plus point to DRG would be their bad-ass skill animations imo.