What Spark Plug Should I Buy For Benz B160?

I have a MERCEDES-BENZ B-Class B 160 1.5 (245.231) petrol and I am trying to buy a spark plug to replace existing once but I see various types like

RIDEX PLUS Iridium 686S0034P Spark plug
RIDEX ULTRA 686S0026 Spark plug

Since both are compactible with my car but not sure which is better.