A perfect comparison is ExpressPCB vs. JLCPCB.
I had used ExpressPCB for a decade and half, and during that interval, the price went from reasonable to eye-watering, specially for a single-off project.
But let’s put the price aside for a moment, and concentrate on the different features available.
With expressPCB, you are basically stuck with a rectangular, 0.060” thick, 1 oz copper, FR4 green board. No slots, nor large holes, nor odd shapes, nor connector cutouts available. No soldermak color options. No thinner or thicker FR4 stock. No board materials different from FR4, no flexible boards, no different copper weight. No filling or tenting of vias. With the Classic version, silkscreen is only available for the top side. Only PbSn HASL finish. No plain holes without a pad. This is from the top of my head, I am sure there were other limitations. The component library is prehistoric, at least it was the last time I used it.
And when I have had issues with my order, which to my embarrassment I must admit have been several, I have always found that the JLCPCB’s customer service is heads above that of ExpressPCB.
It is not only the much higher price, the only reason that nowadays I no longer use ExpressPCB.