The TS should know what does a 'true/native HD' looks like. Fine examples are Bakemono (it's like purely animated on computers), Mayo Chiki, EF Tales series. While Motto To LOVE-Ru is questionable. I had read somewhere 32" is the limit for 720p but sometimes it would go up to 60". So with below 32", 720 is good enough. Keep it in mind that you must be 5 inches away with a 42" or larger screens (I can't imagine doing that so I stick with 32") in order to see the 1080p goodness. Though sometimes I do not follow this rule on bbt, because 1080p is freeleech

Just download what's best for your hardware, what you download today, doesn't matter in the future with today's pixel count and I don't think I'll re-watch a certain series again after 5 years when I buy a new hardware.