Usually, the only difference in a 6-year and a 12-year WH is the price you pay - you're paying mainly for insurance, and sometimes, a second or longer sacrificial anode. Personally, I'd avoid both the Kenmore and the Whirlpool...if you use the search function, you'll find tons of opinions and rationale - no big need to repeat it all again. Rheem makes the GE WH for HD, and Rheem is among those often recommended. All of these companies make numerous versions which includes varying levels of efficiency and types of flue to accommodate various installation configurations.
Some of them are efficient enough to qualify for a rebate from the utility company - check with them for details - the difference in price may be offset or even be less than getting one that doesn't qualify, not counting the long-term potential savings.