All OGC interface standards (WMS/WFS/WCS/WPS/SOS/WMTS) operations are stateless and cacheable irrespective of their encoding. So there is no gain or comparison to be made here.
It is moot whether the so called WMTS RESTful encoding is indeed RESTful, as a client seems to require out of band information, i.e. information other than that provided in the hypermedia, which is an anti-REST pattern. So really your choice of encoding is purely personal choice.