Personally I think wait time is also a factor of customer service. And with the amount of time they make customers wait before getting served, I find their customer service very easily beatable.

And there are also reports that they employ the same overpricing tactics on filters similar to AP (you can do a search on CS to read more).
And i never had any problems dealing with TK. Most items are tagged clearly and one price. And the prices are good.
Cathay has such a huge variety. Best to ask for e-quote via their sales email. Good service actually.
MSC has never responded to my requests for e-quote over the years. Bought from them a couple of times, paid over market price for some items. But not obscenely over. But if you really want to buy from MSC, go to the branch near the S11 hawker centre, and talk to the lady boss Florence. Some of the other sales staff are not pleasant to deal with.
SLR-R prices are one of the lowest actually without the need for haggling.
AP is the one you should be careful when dealing.
Well... just my personal opinions and experience.