I have no doubt that the Jayco would be capable of doing parts of the OTL up the Cape, but would think that parts of the track would be a little difficult with the Jayco in tow, more due to the sheer size of the thing rather than the build quality. Last year when we were up the Cape, there were a few Jaycos touring around, as well as a number of larger 20+ foot caravans, so depending on where you want to go anything is possible.
The Camp-o-matic brand as it is now, is not a patch on the older Australian made version, and being a Camp-o-matic owner I am more than clued up on the changes which have evolved with this brand. I would be very reluctant to purchase a new Camp-o-matic knowing that the majority of which is made in China. As much as it pains me to say this, the newer models are not a patch on the older ones, as far as build quality is concerned.
Now how this compares with the Jayco campers, I couldn't say, but as far as I'm concerned both are built to a very strict budget rather than being built to a quality, however Jayco seem to have a very good warrranty backup.
If you are set on buying one of these brands, then consider whether you will be tackling tougher tight track, in which the Camp-o-matic would be best, or if you are considering open gravel roads with a few rougher sections thrown in then the Jayco is probably the best option.