This is a perfect, yet simple enough, example where it would benefit you to ask the Armstrong Retailer why you shouldn't buy Congonleum, and ask the Congonleum Retailer why you shouldn't buy Armstrong. Be sure you get information that talks about thickness, high-heel marks, wear-layer thickness, seams, and WARRANTY!!!
I'm partial to Armstrong. 1) I liked their selection, 2) the Solarium line of vinyl has a 1/8" thick wear-layer, and 3) the price was right. I don't have any pets and only 1 child at the moment. Our kitchen is, basically, 10' x 22'. It's 2-1/2 sheets wide. The better 'grades' of vinyl have a good wear-layer. That means if the vinyl starts to wear or gets scratched, the 'design' goes deep enough into the vinyl that you won't see the damage. That's a nice feature.
Now, granted, no vinyl is perfect. BUT, do ask what the differences is (except price) between the top-of-the-line vinyl and, say, the line below it. At least you'll know if the cost difference is worth it. My best to ya and hope this helps.