I prefer the online relay. It's a lot easier and I can see the whole converstation. It's faster and more clearer instead of the old fashioned text TTYs. I can easily look back and see what was said recently or know what I said in case I accidently said something else. Lastly, I can save the converstation into my computer at ease. Sure, TTYs can do the same thing... but it takes a lot of line-by-line scrolling to find what was said or have everything printed on that tiny piece of paper.
A good example would be a couple of my friends. One friend used a TTY to make a call about something. He ended up with 5 ft of paper with the text printed on it. The other friend used a computer. When he was done, everything he said was only on one page. 
