See for me while Sanderson is left handed, in my viewings Drysdale is better at pretty much everything. I've heard some compelling arguments from people that think Sanderson is the better defender because he gaps up very well and has superior size... But it hasn't been what I've seen. I see Drysdale being more engaged with the play, having much better offensive contributions, being the higher IQ and faster player. He's smaller and a RD. That's it for disadvantages IMO. I project Sanderson as a middle pairing, defensively responsible D. He can PK but not PP at the next level. His skating is great, and he can seperate guys from the puck. Once he has it though, I don't see him having the vision, hands or passing to get it up the ice to our forwards. He's not going to get you controlled possessions and offensive zone entries at the NHL level.
I project Drysdale as a true #1 defenseman and better than anyone we have in the organization. He'd run both our PP and our PK. He's a better prospect than Seider by a lot for me because his skating and vision are just better. He projects as a far more complete defenseman than Hronek for me because of how well he can defend. He's the guy with the fewest question marks and the highest upside besides Raymond (whom has way more question marks) here.
If we end up with too many good RD, we can move one. The talent disparity is such that handedness shouldn't even begin to matter IMO. Drysdale is strictly superior to Sanderson IMO. His skating is strong enough that he can always be between his opponent and the net, angle them to the boards, and when he gets it evade pressure for a controlled exit and then a controlled entry. Once in the offensive zone he has the vision to set up his teammates and lateral mobility to walk the line and get shooting and passing angles.