Ah, but rotational weight is worth more than any other sort, so (ignoring any fitness implications) you're better off saving 300g on your wheels than on your body.
Do your legs not rotate when you pedal?
If you can produce the same power after weight loss, it's always better to lose the weight from body not bike. There are more advantages than just the weight (it's cheaper to lose body weight, you get better heat management, your heart has to pump blood to less tissue so you're more efficient, etc). If you lose body weight you can STILL have a lighter bike too.
Do your legs not rotate when you pedal?
If you can produce the same power after weight loss, it's always better to lose the weight from body not bike. There are more advantages than just the weight (it's cheaper to lose body weight, you get better heat management, your heart has to pump blood to less tissue so you're more efficient, etc). If you lose body weight you can STILL have a lighter bike too.