Al-
I was in the Leung Ting system for 9 years, and from my personal experience I have found that they have some benefits and pit-falls. In my experience, they have a good training curriculum. But they don't incorporate very much lat-sau. Now some people don't care about chinese lat-sau, but those people aren't going to be very good at applying their techniques in combat. Chi-sau is how you get your feeling, and lat-sau is the application to fighting.
the IWTA has some good stuff for training, and they used to be pretty big in america. But they are rapidly declining, I believe there is only 3 major schools left. San Antonio (Sifu Will Parker) - Arizona (Sifu Mike... forgot his last name lol) and Chicago (Sifu Mike Adams)... My problem with the IWTA is the polotics. And they charge and arm and a leg for everything. I don't care what anyone thinks, but it shouldn't cost 600$ (american) a section to learn the knives. I don't have that much experience with the Fong guys, but from the few that I have met, they were all very nice people and trained hard. That being said, if you already have a flavor for LT style WT, you should go check out the A. Fong guy and find what fits you better

... I've had a few opprotunities to meet and greet and train a bit with Sifu Webb, and he is a bad-***. I enjoyed his insight and his well rounded knowledge in the art. But back then I was but a beginner. If you can find what suits your needs and aligns with your sensiblities, that is where you will be the most happy.
Just remember there are so many differences out there that the only way to get it all is tro train with everyone lol... And thats the crux of the matter. Most LT type people (Not saying that Sifu Webb has done or will do this) usually get jealous if you go out and train with other people. Sifu Will Parker (My 1st sifu) had a bad tendency to get jealous and go off on a power trip about how LT WT is the best, so why go anywhere else, even to other people in the LT orginization.
Truthfully, LTWT or the IWTA definately isn't the best, and especially in america. Personally I would go with Sifu Webb, because that is the style I am most comfortable with, and I have no want or need to re-learn things another way. That isn't to say I wouldn't enjoy having a chance to touch hands with the Augustine Fong guys because they have yet another perspective that can help you on the road to understanding yourself better and your martial arts better.
I would however urge you if you can find a City Wing Tsun group (Sifu's Glenn Tillman & Ramfis De Pena, who are two close friends of mine) to go train with them. They live in San Antonio, and to me the Alex Richter approach is the best that suits my needs and aligns with the way I want Wing Tsun to be for me.
Lol this is just basically a long-winded reply that says: Try them both out and see what fits, then go with that
All the best in your descision and training!