Is there a resource to select based on WS or weight or???

That's a good question and one I ask myself often. You can download servo charts that will help you some. There are so many options out there it's hard to say, "get this if that" and get this if it has this, etc.
I have built about 7 planes now from kits....all with wingspans from about 48" to 72"....all are "beginner type" planes that aren't going to be flown real hard. I put the same servos in all of them (Futaba S3004 on the throttle and S3010 everywhere else)
They have all flown great. But I ask myself....did I need S3010? I have no idea. Hinges and hardware I always err on the safe side. Usually the hardware comes with the kit and I have never had a hinge fail or any of the hardware fail for that matter.
I'm sure there are a lot of guys out there that have more knowledge to answer your question than I am but its food for thought.

There are more variables than that. Speed and the style of flying are big factors too. Honestly though, most servos are significantly stronger than they need to be. .60 sized aerobatics planes were flown in the 70's with 25 oz in servos that were huge and heavy. Now a 1 oz mini servo will put out 70 oz in if I choose to spend the money on one of the better ones.

For .40-.60 size trainer and sport planes, you can't go wrong with a standard size analog ball bearing servo. Specific ones include the Futaba 3004 and Hitec 425.