I learned to fly on both of those planes, but more on the lt-40 and I prefer the lt-40. The lt-40 is more fun for me to fly now and is capable of pretty high speeds and many basic aerobatics. The senior is a little easier to fly, and fun for some people who just like to fly around in slow circles and do a couple of loops. I'm guessing your planning to buy an arf and I feel that the lt-40 is a better built arf. The senior arf can be bought as a Sig or World models plane and since my dad has one I know what it's like. The wing looks like it could rip off on a high g pull out. As you may know, the arf senior comes with ailerons but they have to be mixed with the rudder to be effective. So I just happen to prefer the lt-40 but your flying style preference might be different then mine. Whichever plane you buy, I would reccomend either a tt .46 pro or os .46fx to power it. The lt-40 will preform much better with this engine. The senior could easily take a .61 too.