Should i get a S8 or a S9 ?

I have a galaxy S7 for like 3 years now and it got pretty beat up. I would like to upgrade but i dont know what to get.
Durability is always a bonus because i work more outside and the phone will be subjected to the elements, mainly dirty hands handling it and a few scratches ( but i will buy a nice case for it. I've read somewhere that the S9 is more sturdy than the S8, so the question is....

Is it worth spending more $ to get the S9 or should i settle for s8 ?

And what is the deal with dual sims ? from what i see i can get it cheaper with dual sim than single. Is there any difference at all ( size, performance, etc ) other than it accepts two sim cards ?
HTC Crew
Armwrestling Crew

"He who laughs at himself never runs out of things to laugh at"
Adolf Hitler - 30 April 1945, before pulling the trigger.