An aborted switch of labels from Harvest (HAR5079) to Warner Bros. (K16336) for "I Wish It Could be Christmas Everyday" b/w "Rob Roy's Nightmare (A Bit More H.A.)" meant that the Wizzard single had much less time to build up a head of steam than Slade's tune hence its final position of #4 was all the more remarkable. Yet (as shown above) whenever both records have re-entered the singles chart together thereafter, the Wizzard track has managed a higher placing than the Slade song ten (10) out of eleven (11) times.
Yours Truly KJS will (obviously) always prefer "I Wish It Could Be Christmas Everyday". Both songs are perennial faves, equally loved by many and not necessarily in competition with each other. If nothing else, the inclusion of downloads and streamed content within the Official UK Singles Chart since 2006 has given Roy Wood and Wizzard the edge in terms of chart performance.
Until next "Time" in the ELO [and related] Universe ... KJS ... 01-Jan-2017