I don't see where either method would be a violation, the NEC has determined these supply side conductors as feeders, in a recent technical opinion I received from NFPA in reference to grounding, NFPA responded that NEC 690.43 (A) applies and the only articles in 250 that can be enforced is 250.134 or 250.136 (A), I don't see where either of these code sections would prohibit SEU cable for a typical residential supply side connection, article 250.134 allows 250.142 that permits the grounded conductor to be used for grounding enclosures on the supply side and 230.40 exception #5 would also seem to permit this.