The tough question here is what advantage in exploration will the Carrack have over the 600?
Carrack is going to require more crew to properly function. . .
I don't think the question of best explorer is between the 600i and Carrack. It's between the Carrack and Polaris. So long as you have sufficient crew (and you always will, Glorious Leader), I think bigger is better.
I am just unsure how the Carrack is better than the Polaris at exploration. One supposes it can do better scanning. We'll have to wait and see.
I'm not even sure either of these will be the best explorer. On deep excursions, most of your time will be in quantum, so the best explorers will probably need Cap sized Q drives. Given you will never have trouble finding a crew, I think you might consider the Idris P as an explorer. One can imagine putting half dozen rovers on the ground, along with half dozen X1 Force bikes, and you can supply support for any number of utility birds. The same crew you use to explore, you can use for battle, and that crew will all be good at their jobs if they spend enough time on the one ship.
It does not make sense to me the Idris has L radar, and I think that is a remnant of an old system. If I found that the Idris really has a smaller radar than the Polaris, then I guess I would rethink.
So for example, you can fly the Idris out QT for a full day or two, and then anyone who wants to join you and has a bed can fly out. Save the hanger for birds with no beds, like the Tracker.
An Idris could support 315Ps, Mustang Deltas, Sens all of which might take a week to reach the Idris, but since they have beds they could reach you, and after that they can resupply and fly off the Idris. Lancer Durs could do the same, though it would take them less time to get in theater.
One bird becomes the support ship for all those who want to explore a region, so you begin to think of the Idris as a highly maneuverable station, with constant activity of little birds coming and going, which is much more fun than being alone, IMHO. The Idris owner could actually lease support services for a small fee and a portion of any significant find, so everyone gets something. If you want to stay for more than a week or two, then you need a StarG to come out, but it would be much safer with an Idris as a companion. With a StarG gathering fuel in situ, the Idris could stay out indefinitely.
I organized planetary search Ops for both Ailon Nova Guard and The Wraiths in SWG. I'd be happy to show someone how to organize very large searches with GoogleDocs. If you really want that
Krath transporter technology*, you need to think about the long searches.
* Hell no, I made that shit up. Transporter technology?! Are you kidding me. . .what? Wait. No, really?