UA Explorer has 2miles/$ on UA spend (and a 10k bonus at $25k spend). The only other real benefit I see for 1k iis the primary rental car insurance (and the two lounge passes)
Sapphire preferred is 2 points/$ on all travel and dining ( plus the 7% bonus). It also has more flexible transfer options.
Depending on your spending patterns, one or the other should work out better for you. You may also want to look at the Chase UA club card.