I think the kind of food Kopitiam serves is both unfamiliar to a lot of people and easy to like, which makes it more popular - and talked about - than good (although I also think it's pretty good).
I think that sums it up. I think it's telling that of the two critics, Sutton has been the more vocal cheerleader, whereas Sietsema, who would be more familiar - he likes it, sure, but hasn't been quite so over-the-moon. While he's never done a side-by-side I got the impression he preferred the Pan Mee at Let's Makan.
I do also think Kopitiam is pretty good. The oyster omelette is a fave. The Pan Mee I've been up and down on, I've had it perfect a couple times, and a couple other times I've had the noodles all stuck together in a clump.