1) Defining old tree as basically over 150yo.
2) Most serious old tree tea is not very available, and very expensive when they are. Doubly true when we're talking anywhere north of Jingmai. There are not-so-great old tree tea trees (and areas) as well.
3) Other old tree tea is quite overpicked (or stumped for easy picking) and is a poor performer relative to what the performance should be.
4) Many brands seem to use arbor grown trees (da shu cha) in place of lao shu cha. Or they cut with that leaf.
5) Therefore, there is really no way to tell from observing dry or wet leaf whether that's a quality leaf or not.
6) In the mouth, unless you are pretty experienced (or you get a stunning example), it can be hard to tell or prefer old tree tea, especially as people have upped their game to get quality leaf from younger trees.
7) If people want to educate themselves, I suggest getting samples of normal 7542 and special grade 7542 from between '96 and '03, with similar storage. Many of the special grade teas should have some old tree teas sprinkled in. Good tea was very, very, cheap back then, particularly before '02, and only started to be expensive from about '04.
Broadly speaking, after 2009 and definitely after the late spring of 2010, great examples of old tree tea became rare. Sanhetang's product quality fell by quite a bit after 2009 for the run of the mill tea, and to get the nice stuff, well, that was over $200 a bing in 2010, and almost $300 in 2011, and now, about $300+ for the tea with some buzz in the mouth and throat. There are still some quality old tree teas normal people can buy with some oomph, but they mostly come from areas like Bangwei, which cannot hope to match the best Mengku, JingGu, or Jingmai teas. Unless you're buying the leftover teas from various shops--and they're leftovers because they aren't from top areas, the top stuff, or they're blends, you really shouldn't assume most tea you get is exalted unless you paid lots of money to people you're pretty sure has the connections (particularly wrt to anything from Banna, it's locked down).
9) I talk about the "good stuff" because, well, there are plenty of old tree teas out there. What people who aren't trying to flatter themselves and who want to buy great tea ask for, is for quality old tree. I've had the XZH '09 Diangu and the XZH '11 Diangu. Same place, same brand, not nearly the same quality. Old tree, though, in both cases. If your priority is price, what you really should look for is da shu or shengtai, given that most "affordable old tree" is either not so or from dead cheap areas. Sometimes, if the brand is good, old tree is simply an indicator of quality.
10) Will a plantation tea ever beat an old tree tea worthy of the name? No. Certainly not over a number of sessions. If a plantation tea is beating an old tree tea, there are a number of reasons that could be so. First of all, you may not like that particular old tree tea for some reason not relevant to all old tree tea. The tea might not be good, or it might be poorly stored. You might simply not have developed a consistent means to appreciate old tree tea. Tea drinking is about expectations. If you're expecting plantation tea, you may drink plantation tea qualities and miss old tree tea qualities from your session. Plantation tea is what it is pretty much because it's rather limited. The aroma won't really endure. The taste hits narrowly. The aftertastes are rather short. Typically, young plantation tea has an obnoxious green edge. Better cared for plantation tea can approximate good gushu, but they simply don't have the registers gushu has.