well if you want to run Pro Tools, you don't have a choice as the 1804 won't interface with PT.
the tascam has twice the number of preamps as the 002, which only has 4. the 002 will interface more channels than that, but you'll have to buy external pres with digital outs to use them.
the 002 also has a control surface intergrated (perhaps you were looking at the 002r, the rack version with no control surface. the only difference between the 002 and the 002r is the 002 has the control surface. same number of pres, inputs etc.)