If you don't have the money - go for the Diamondback explorer (costs only a few million to fit)
If you have a decent amount of money - the Asp is pretty much the perfect explorer because it has a huuuge glass canopy and the look from it is unobstructed, and pretty much amazing. Costs 12-14mil to fit for pure exploration depending on the discounts. Check
my Asp out (there's a link to the fit on the bottom)- I just came back from Sag A* with 94% hull left.
And if you're packed with money - go for the Anaconda. It has the best jump range, topping it around 38-39Ly. You will probably need 170-180mil though