the usuall answer is that it depends on the product but you can pretty sure exclude b no matter what the product is.
This is coz you need to give the reseller the motivation to promote your product more than others, normally - if your product is one of a few or many this will be difficult.
Find a sales co-founder who has experience in that particular field, he can as well give you the insight into the market
Though you should have a few testing customers before you start big sales activities.
And regarding co-founder in general: don't bother about giving away relevant amount your company shares. If you have full trust in the person capabilities and ideally network then you should be fair on not try to get him as low as possible (in many cases co-founder teams break up if the shares distributed differ very much and if it does not mirror effort and responsibility).
100% of nothing is worse than 1% of 50 million