I am about to put weed and feed on my lawn in next 2 days.
for 40LB bag, Scotts weed and feed is $50, And 50LB bag of store brand(Menards) weed& feed is $26.
Is it worth going with Scotts? Numbers on both the products are same '39-0-0'
I'd suggest that you use neither. A better approach is to do two separate applications. First fertilize. Then, about two weeks later, when the weeds are growing like crazy, use a weed killer. Unless your lawn is mostly weeds, I would get a broadleaf weed killer and spot spray only where the weeds are. But don't spray if daily highs will be above 90 (maybe 80, check the label).
The reason for doing it in two steps is that the weed killers are absorbed through the leaves and work best when the weeds are growing vigorously.
As for the brand, I don't think it matters. You're looking to apply a specific amount of N,P,K and those are the numbers on the bag. It doesn't make a lot of difference who made it, it's what's inside.
I've used Scott's, Lowe's Sta-Green and HD's Vigoro. I've found that in my climate, Scott's (granular) acts more quickly, but Sta-Green (which is pelletized) feeds more evenly and lasts longer. The problem is that the only Sta-Green products (made by Spectracide) I can get are Phosphorus-free which has a noticeably poorer result in spring feeding. As a result, I tend to use equal parts Scott's (with Phos) and Sta-Green (without Phos). Best of both worlds, I suppose. I agree with BPGREEN that nothing beats spot treatment with a liquid broadleaf weed killer. It's also nice to know that you're not spreading weed killer where it isn't needed. If you have a lot of weeds, definitely get a backpack sprayer and use a mix from concentrate. It's been a great investment for me on my 3 acre parcel...you can get 3 or 4 gallon backpacks for under $100. It saves time and your back.