What was your source for the plants? In other words, did you grow them yourself or purchase them?

Were both varieties from the same source? Without knowing the complete facts about the plants you have, at best we are guessing....

And now I'll go out on a limb and make a guess:

Did the Cherokee Purple have fruit on it when you planted it? If so, that could be the reason it isn't growing as fast as the Brandywines. Instead of putting its energy into root and plant growth after transplanting, it is trying to produce fruit at the expense of the overall plant growth. This is one reason you will usually see advice to remove blossoms and fruit from a tomato plant when you transplant them.

Betsy

Comparing different varieties for growth rates is very mis-leading and basically pointless. Just as the fruit produced is different so are the growth patterns.

The size of the plant is determined by its genetics in addition to the growing conditions. So IF you insure they are both given the same growing conditions then it is the genetics of the variety that make the difference. CP never reaches 9 feet, maybe 6 feet. It is normally a smaller plant than BW even at full growth.

Dave

well i live in your neck of the woods and my cherokee purple plant has done the same thing. it and mr stripey are the weakest looking varieties in my garden.