I have searched through number of discussions and I did find one really useful review:
[ti-80 is gonna have a much crisper, precise feel, while the RDX-500 is gonna have a much softer (some say buttery, I say mushy) feel. TI-80 cuts through the air better and feels more maneuverable; it's got a thinner box beam. The RDX will feel more "solid" stock on groundstrokes, but will feel less potent on serves and volleys. Ti-80 with some lead tape will feel plenty solid though; it just starts out really headlight and thin in the hoop. Personally, I much prefer the TI-80 as I can't get the pop on serves with the RDX that I want, and I tend to prefer a more raw precise feel to a muted, dampened, or vague hit. Also, since the TI-80 starts out so headlight and swings so fast, there's more room for customization with lead tape to find the right swingweight and balance.]
Any other thoughts?