Oh, yes, I forgot to say ... I am of the pre-wash abuse mindset!
I see synthrapol and colour catchers as a quality control ... or safety check when uncertain! So, thus why I wondered what you thought of the two in comparison.
What I like about colour catchers is, that I have "evidence" ... it's either white or not. I haven't used synthrapol, but I bet I'd always be "wondering" if there was any colour running around in the washer!