"Hello, I'm interested in talking with you about studying Tai Chi but I'm not sure about what style. I have studied a "short form" and concerned about taking on learning a Long Form, can you explain these differences in things a little?"
First of all I would welcome you in my classes and like to state that I have also done "simplified" and "short" forms myself. If you could indulge my quip here as I paraphrase Mark Twain I should explain that it would take too long to write a "short" answer to your question and so I have to write a "long" one. My teacher has addressed this very well by explaining that the very few old Grandmasters in China dealt with the popularity of Tai Chi by "simplifying" the Long Form. This "simplification" meant it was taught with no "internal discipline" and no explanation. Later these sets of movements were abridged further to containing even fewer movements. These "Short" forms of different styles have become very popular in this day and age. He tells me that the popularity conundrum still exists and the problem is to still teach only a few movements but he has found a new approach to do this. Yes, we teach fewer movements in this additional approach to our "long form" instruction but each movement is to be studied in depth with "internal discipline" as the essential component. The thinking of the "short form" was "less is more" and our approach can be summed up as the same "less is more" with the understanding that teaching a lot of movements will not bestow health benefits. But teaching a few movements with an emphasis on learning even one internal movement very well will give much in the way of health benefit. You can see an introduction and a subsequent series of these movements here starting with the "Introduction" then "Tai Chi Exercise 1 through 11":