I've ordered about 50 different CPs over the last 3 months from about 8 or so different online nurseries and I've noticed that the potted plants always grow better and bare root ones take at least a month to start hitting a good pace.
It's especially noticeable in Nepenthes where bareroot often means additional pitcher loss. The potted Nepenthes I've gotten through the mail consistently either a)don't lose any pitchers at all or b)lose the pitchers they have more slowly. This is a big deal because the longer they have pitchers the more I can feed them. And I've definitely noticed that more fed pitchers = faster growth. It's particularly sad when I realize that a given Nep can't be fed for awhile and this is being prolonged by slower growth causing new pitchers to form more slowly and ultimately being smaller when developed. This also means less food in the pitchers and slower growth for quite some time.
You know the plants' growth is exponential. If it is slowed down for 3 months and another of the same plant and original size is not it literally does result in a smaller plant 1,2, or 5 years later.
I think a big part of the problem is that the roots we see on a bareroot plant are not extracting nutrients from the soil. It's the smaller root hairs we don't see that branch out into the media that do this. So a bareroot plant is both being nutrient starved through it's roots and has to expend it's stored energy to reestablish those root hairs. A potted plant just keeps growing at it's steady uninterrupted pace.
So it's two fold; less nutrients absorbed through carnivory as well as less nutrients absorbed through roots and then of course the chain reaction in slowed growth these cause.
I'd rather pay a few extra dollars for potted and have a bigger stronger plant.