sleeper and dirt-scratcher gave good input so far. I will add that the Explorer II was amongst the best in the entire Explorer evolution. From the XS (the first explorer) to the 3030 (the present incarnation), the Exp. II is tops.
It can be debated as to whether or not the 3030 has "added depth". There's an ongoing debate there, that I won't go into here. And sure, it's nice to have waterproof, and perhaps some added target recovery speed, etc... with the 3030. But you're talking VVVEEERRRYYY negligable specialty niche differences. For most of the hunting I do, the Exp. II is going to do everything the 3030 can do, at identical depths. The advantage of the Exp. II is the well-loved tones. Silver just sings out so nice in turf hunting. Yes I know it's debated that the 3030 has all sorts of user options, and can be made to sing just as nice, blah blah. Also the Exp. II allows you to have an in-line probe, while the 3030 does not.
If I were you, I'd go with the Exp. II.