I recently purchased the Raymaine L1260DRC chart plotter and high def FF ("the black box").
http://www.raymarine.com/raymarine/P...roduct_id=1243
It uses C-MAP charts. I like the charts alot and is one of the primary reasons I considered this machine. They are updated every six months. IMO they are very nice. You can even subscribe and for a small fee get your chip updated up to 2X per year if you want. (They claim them make 800-1200 mods to the charts per year) After speaking to several people in the e-chart business, from what I understand (I don't know this for a fact), but Garmin bought a Russian company to do their charts. Their latest charts are based on data that is over 4 years old in some case much more. More then one person told me this. Generally that should not matter since the bottom does not change much but in some locations it might. Also there are a number of minor changes year to year on buoys ect.
The unit I have has a 10.4" screen and I can zoom to 1/64 of a mile which is plenty IMO. It has a very nice expandablity feature and I cant wait to get another screen to have separate depth and chart/radar and FF on their respective screens. I am just getting use to it and there are a few quirks that I have to find work arounds to.
For example, the desktop software from CMAP works great...and I have entered over 300 fishing coords from LI to NH. and I can save the to the cmap card "user card" but the unit does not rec the format...It says I can do this in the manual but need to debug the problem...this is upsetting. Also, Raychart has its own desktop software called Raytech and it is way more then I need...(actually it address the on-board and at home laptop issue and making your laptop another monitor capabile of displaying anything...it costs about 400 and I may end up getting it in the end. For now I have the cheaper CMAP software and a CMAP USB drive so you can take your CMAP chip and load it on your desktop...this works nicely and which allow nice plotting of routes, waypoints, ect and managing them and the user cards.
Mine is the HSB2 unit and is pricey but they make a SL (stand alone) model (whick looks and acts the same) with out the networking that is more reasonable in price. I like the ergonomics of the machine and the depthfinder is the best I have ever seen on any pleasure boat . I have seen some 19" monitors on commerical rigs that are unreal but for pleasure and light duty commerial this is really nice.
Right now I think the best deal in a big stand alone CP out there is the Standard marine 10.5" (landscape mode). It is big and clear and is *only* 1999 in the stores (a couple hundred cheaper online) . It uses CMAP but IMO is more cumbersome to use. The menus and sub menus are a little awkward, but the sceen is very nice.
What I ened up doing was first to decide what chart system I wanted then look at devices that used them (not visa versa). Most of the units out there are good and have the basic features ...If fact my handheld does almost everything my big machine can do and in one case (having to do with mag headings) it can do more then the big unit. The Raymarine would "like" a electronic compass in the loop. The Navionics (gold) seems nice too but I only looked at it on one machine.
As far as "rock accuracy" I have not really tested that just yet. It seems pretty accurate when I passed thru a very narrow inlet it has me positioned in the right spot in the inlet...within a few feet anyway. But I have not gotten down to indiv rocks just yet. Most of the echarts are based on the latest uscg paper charts so I don't think there will be any big differences. I plan to head to the Cuttyhunk area soon and will work Robinsons hole which should be a good test for rocks...if I don't come back you can assume it ain't too good.
Anyway, good luck on your decesion.