I had some Dexter lodgers and I thought them too small, and really the bigger cows do not take much more keeping
You must live in the land of milk and honey!
There were Dexters here when I came. It was a challenge trying to manage them and the Jerseys together. In the end the Dexters had to go because we couldn't milk those, we couldn't manage them all together, and we don't have enough ground here to keep two separate herds.
The Dexters were very hardy, the Jersey not,
The Dexters, being smaller, are very light on the ground. If you are in a wet place, as we are, the physical weight of your beasts makes a
huge difference to keeping them over winter. And if your ground tends to mud, bigger beasts will poach the ground much more quickly and deeply.
The Dexters make good use of shorter grass, which the Jerseys wouldn't attempt to graze.
when it comes to sending them off for beef the slaughter costs are the same.
Slaughter fee yes, is per head. But butchery costs are mostly per kilo.
I have found that crosses out of the Jersey are a good size by 10 months, so for us, it works well to send the calves off in November, so we don't have to winter them. The meat is fantastic. A Dexter at 10 months is no size at all, I think you would want to take them through a second summer. But the calves are hairy, tough little creatures and can outwinter down here as long as there is good natural shelter. So if your ground can take it - and you have enough of it for followers over the summer, plus for making enough hay for stirks through the winter - and your winters aren't too vicious, needing two summers might not be a problem.
I should mention that our cows rear their own calves up to 5 months at least. I don't know if I would get such fit animals by 10 months if I took the calves off and reared them on a bucket, even on their own mum's milk. And I have found that weaning them before 5 months gives them such a setback that again, I think they wouldn't be ready by 10 months.