The cents or pence debate only applies to American comic books and not British-produced comics like Dandy and Beano.
In the 1940s and 1950s, some American comics found their way over to the United Kingdom through American servicemen, through friends and family. Throughout the 1950s, the adventures of Superman and Batman and the like were reprinted and re-packaged for (mostly) the British and Australian markets.
In late 1959, the first American comic books were officially imported and distributed to newsagents and other magazine outlets. Batman #127 and Superman #132 (both cover dated Oct 1959) led the way in small quanities. The floodgates opened the following month with cover dates of Nov 1959. The quantities ordered would probably have been quite small as retailers tried out these new comics which would take shelf and counter space away from the vast array of British comics that had been sold for decades.
British editions of American comics were printed at the same time, on the same paper using the same machinery. The proportion of British copies was generally somewhere up to 5% of the print run but was probably much lower in the early days of Marvel and DC UK distribution, nearer 2-3%.
At the end of a print run, in the case of the early Marvels, a 9d (ninepence) cover price plate was substituted in place of the American 10 cents. For DCs, the cover was hand-stamped. The stamping varies - some can be quite light, others quite heavy and some can be stamped twice when the person concerned missed the first time!
Early Marvels have additional distributor information in the indicia - a single line saying Sole Distributors in the United Kingdom - Thorpe & Porter Ltd. But this needs comprehensive checking. There are also a few instances on 60s Marvel comics where the British cover paper seems to be fractionally thinner than on the US edition (eg Fantastic Four #56) but this again needs comprehensive checking.
Rather than call all these comics UK editions, it would perhaps be more accurate to call them 'pence copies' or 'British priced variants'. Overall they cannot be said to be a reprint of the US edition or, as such, inferior .
In fact it could be argued that in this day and age of variants and alternative covers offered as retailer incentives, British pence copies of American comics are much rarer and have an attraction all of their own. In very high grades or for key issues, one could argue that British pence copies offer value for money.
Some UK collectors prefer UK pence editions of American comics as that 's what they remember as children.
Other collectors prefer the purism of the cents copy, that an American comic should have an American cover price.
What it comes down to is condition, personal preference and spending power.
An early copy of Amazing Spider-Man in FN cents condition currently may be priced the same as a VFN/NM pence copy. If, for example, you have always wanted an Avengers #1 but see a cents copy is over a thousand pounds in VG condition, would you rather opt for a higher grade, better-looking pence copy for the same amount of money?
Sometimes, though, a cents copy just looks better . For example, some 9d and 10d cover stamps on early Marvels and especially DCs can be very heavy and randomly splattered on a character's face. Many 1970s Marvel comics were ND or Non Distributed in the UK and thus were always cover priced in cents. There may have been the odd issue or small run in a series which was distributed and have a British cover price before becoming ND again. Some collectors may feel that for a consistent looking run, all the copies should be cents.
Traditionally American collectors and dealers have frowned upon pence copies but increasingly they have come to recognise the rarity of these pence copies and perhaps see a potential treasure trove.
Indeed there have been reports of American dealers buying British pence copies and charging a higher rarity value!
It remains an inescapable fact that at the moment cents copies are valued higher than pence copies. Currently, general issues of pence copies seem to be valued at about a half compared to cents copies in the lower grades. From about Very Fine condition onwards the gap tends to widen to perhaps a third of the US value. Key issues in cents in very high grades tend to be stratospheric!
It is difficult to compare with very high grade pence copies and cents copies. Sales of, say, Very Fine/Near Mint Amazing Fantasy #15 or Journey into Mystery #83 pence copies are few and far between.
The highest CGC graded Amazing Spider-Man #1 pence copy was advertised in 2010 at the American cents guide price but only attracted bids at half that value. It remains to be seen if that gap between cents and pence copies will narrow or widen.
For the purposes of this guide, all values are in pounds sterling for pence copies. If a comic is only available as a cents copy, that value is given. If you have a cents copy of something that was available either in pence or cents, it would be reasonable to think in general terms about doubling the pence copy values.
The disparity in prices between pence and cents copies is absolutely at its greatest with major key and number one issues in very high grade. A 9.4 Near Mint, cents copy of Amazing Fantasy #15 (the first Spider-Man) has sold for $227,000. At what fraction would a Near Mint pence copy fetch if one ever became available for auction or sale?