The big issue with the B8350 is that it uses cartridges containing three inks each. The colour cartridge is cyan, magenta and yellow, which you use either with a black cartridge or, for photo work, a three ink 'photo' cartridge (which is black, light cyan and light magenta).
The colour cartridges are supposedly available in three sizes. There's also a three ink black and white photo cartridge for black and white work.
The cartridges are not that big - see here
. With these triple colour cartridges, you have to throw away the cartridge when one colour is exhausted.
The big colour cartridge for the B8350 appears to be C9363EE (Â£17.27 from LambdaTek), the photo cartridge appears to be C9369EE (Â£12.27 from LambdaTek). If the HP coverage figures are right, each 6x4 print costs 18.1p in ink (including VAT) - plus the paper. By comparison, the admittedly more expensive to buy B9180 costs 13.7p in ink (including VAT) at current LambdaTek prices using HP coverage figures; the B9180 uses pigment ink compared to the B8350's dye ink and on the B9180, each ink is in a separate 27ml cartridge.
These comparisons are made using HP Advanced Photo Paper Glossy, which is 6.2p per 15x10 sheet from LambdaTek if you order a 100 sheet pack (Q8692A). In other words, the B9180 comes out at 19.9p per 15x10 (or around twice the price of PhotoBox ignoring the P&P), and the B8340 at 24.3p per 15x10.
Advanced Photo Paper Glossy arguably isn't the best paper for dye inks, but is the only one of HP's mainstream photo paper ranges that is nanoporous rather than swellable, and therefore suitable for the B9180's pigment inks. HP recommend their Premium Plus photo papers for dye ink models like the B8350.
Obviously running costs alone are not a reason to choose between models, but I dislike printers with multiple colours per cartridge and all the printers I still use, with the exception of the portable DeskJet 450wbt which receives only very light usage, uses single colour cartridges or tanks. (My printers are an HP Photosmart Pro B9180 for all photo and plain paper A3 work, a HP Color LaserJet 3800dtn for A4 work, and a Canon i865 which is only really used for CDs since I bought the B9180).
The B8350 uses Vivera dye ink rather than the Vivera pigment ink of the approximately twice as expensive B9180. The B8350 can be had for Â£200 from LambdaTek (I don't have shares in them, but their prices tend to be amongst the lowest, and I bought my B9180 from them).
However, the cartridges on the B8350 are just too small for my liking. Even if you only print A4, there's 4.16 times the area on an A4 sheet than on 15x10, which means that on HP's figures, the photo cartridge will only last 31 prints. If your prints happen to exhaust one colour quicker than the other two, you may find yourself throwing the photo cartridge away every 20 prints. On A3, things are twice as bad.
If you have the budget, I'd go for the B9180 rather than the B8350. However, if you're a very low user and don't necessarily want a pigment ink machine, the B8350 may be worth a look.