It's already been hinted at or even said outright in this thread, but I'll just sum this argument up as succinctly as I can:
.COM is king and will almost always be king because of type-in value. The majority of web users will first go to the <keyword>.COM before any other domain (if they even type-in another TLD).
.NET (and other TLD's) are able to compete evenly with .COM's in the SERP's with proper SEO - so for development purposes a .net or .org is as handy as a .com if you can't grab the .com.
However, you ask about RESALE as well as SERP's. To understand why .COM's command a higher price in the aftermarket we turn to the current method of domain name valuation. Right now, many domain investors use scripts or formulas for determining the value of a domain (which account for some multiple of Traffic*CTR*RPC or EPC) . A .COM gets the aforementioned type-in value. This type-in traffic can be monetized, so a domain such as Banking.com vs Banking.net will receive far more in the aftermarket due to this extra traffic. More traffic often = more revenue. More revenue = higher price at sale time (due to multiples of revenue being used as common valuation tool).