Kenko PRO 300 V.S. MC4 TC1.4x with Tokina 10-17 FE

http://www.kenkoglobal.com/TP-PRO300AF-DGX1_4-2X.html

http://www.kenkoglobal.com/TP-MC4AF1_4X-DGX.html

I found Kenko released 2 types of 1.4x TC, namely Pro 300 and MC4.

Which one is the best with Tokina 10-17 FE for underwater using?

The Pro 300 is a 2 model lines above the MC4. It has 5 elements vs 4 elements and should in theory be better optically.