Personally I'd rather have more options. I've had a Cutter for about 6 months and I spend more time flying my Courier, only getting the Cutter out when I feel like doing some trading. I recently got an Anaconda for combat and long range travel (as in, fly somewhere with the huge engineered jump range and ship my Courier over to do what I need to do there).
In about two months of screwing around and doing whatever missions pop up when I'm in the mood, I made about 60% progress within a single rank for the Feds, at that rate I'll never have access to a Corvette (or even the Gunship). So, a circuit of Fed rank grinding here and there just speeds things up. That way in a month or so if I want to fly a Corvette I can, if I don't I won't.