Rudyjr,
I went thru your exact motions last year with my new workplace Exmark with 23 hp KAW. Same canned speech from their tech. guy, except he said even SM oil is suitable.
If you wish to ponder this more, visit lawnsite.com for the "professional's" view. There, you will get more anecdotal stories of "My (insert: self, friend, father, etc.) used (insert: brand x,y,z, weight 10Weverything) and it ran for 8 gazzion hours trouble free. There is no "best" answer.
Generalizing, KAW still leans towards 30 wt.("maybe" consumption with 10w30) and Kohler Command recommends 10W30 due to its lifters.
We have had heated debate here wondering if SM additive levels are suitable for air cooled engines. Choose your side/belief.
Exmark (FAQ and service tips) says to break in your engine with dino (another debate...any where from 0 hours to 250 hours(Exmark)).
I chose to use Rotella 30W (SJ) for the first 100 hours (I'm chicken/warranty) and if I switch to synthetic it will be Amsoil ASE or ASD so I don't have to ponder 30 vs. 10W30. I think the ASE is a great choice for those "on the fence".
Everyone "seems" to agree that the one thing synthetic really does is reduce operating heat of air cooled engines. Less wear, extended drains, etc.. are still debated. Exmark as well as all auto MFG. recommend not changing OCI intervals with synthetic.....CYA I imagine.
Good Luck......are you "by the book" or "seat of the pants"....that is what will guide your decision.