I don't have the Ontario 499 (Civilian version of the JPSK) but I do have several of the various government models of JPSKs made over the years, including a USGI Ontario JPSK. I also have one of the Colonial MK1s. I would pick any JPSK, including older Japanese made versions (PIC, Valor, etc) over the Colonial MK1. Every JPSK I've handled, including some that were in very rough shape would beat the Colonial. The Colonial handle is a light weight plastic and it just "feels wrong" in my hand. To me, it feels very out of balance. The steel may be very good. I wouldn't know because I have never used it for anything. I got it cheap on the "used" market, so I haven't been anxious to get rid of it, but if it somehow got lost, I wouldn't be heartbroken.
For a MK1 that is much better than the Colonial, go with a Kabar MK1. The variations they produce are models 2221/2222/2225/2226. 21/22 are all black, kraton handled, plain/combo (partially serrated) and come with Kydex sheaths. 25/26 are traditional stacked leather, plain/combo edges and leather sheaths. Any model fits in either sheath type.
I prefer the Kabar MK1s to the JPSK mainly because I don't have a need for, nor do I really like, the spine serrations.