Posted the very same question two weeks ago-look at the responses I got. Choose your plotter first. In the end I went for the Simrad CP33 and C-map. I hear prices are set to become very competitive.
C-map cheaper? for updates maybe (with club c-map)
Navionics do huge <A target="_blank" HREF=http://www.navionics.com/Europe/Catalogue/ukG_xl3.asp>XL3</A> areas for £220, prob bigger than many of us need.
normal large size aren't any cheaper yet, but this may change.
C-map areas perhaps more convenient (depending where you cruise), but I can't see a huge price advantage.
Garmin announced 2 new plotters recently (3006 & 3010) so don't pay uk prices for the 20-series....garmin reduced the price of these so shd see more discounts here soon.
Rumours are that Navionics are about to do some sort of three for one offer or something similar, and that C-Map will have to follow. I paid £109 for a map covering Brighton to Gt. Yarmouth which goes right across to Holland and France and will probably see me through the summer. What to watch out for is that the same area may not always have the same smaller maps--mine loses detail after Tilbury on the Thames where as others are detailed further up the Thames.
Rumours are that Navionics are about to do some sort of three for one offer or something similar, and that C-Map will have to follow. I paid £109 for a map covering Brighton to Gt. Yarmouth which goes right across to Holland and France and will probably see me through the summer. What to watch out for is that the same area may not always have the same smaller maps--mine loses detail after Tilbury on the Thames where as others are detailed further up the Thames.
less detail on the navionics xl3 cartridges is something I've asked navionics uk about- no reply yet....a years or so ago c-maps superwide of the south coast missed several large scale charts which were on the local ones.(according to c-map's list)
c-map & bluechart advantage is that they're quite specific about exactly which charts were used to make up each area, so it's possible to check that the available large scale charts were actually used.....whether or not this always equates to detail on the screen is debatable, but it's a start.