As was mentioned dairy bull calves will be the last expensive to buy, once made into steers they will grow into good beef.
An Angus will gain weight a bit faster then a Holstein.
As far as the taste it will depend on what they eat.
If they are grown on good high quality feed they will be good.
As far as age to butcher 14 to 18 months is a good average, you can go sooner or you can go longer.
With 20 acres in KY you should be able to grow 2 or 3 easily. If they have to walk up and down hill to get to water
they will grow slower and be a bit tougher. You can finish on good high protein hay or grass,
I prefer a good bit of grain at least the last few months.
If you have kids that want to get into 4H or if you have an active Grange Chapter or FFA in school it can be a good project for them.
It will not save you any money over store beef, but you will know what it got fed.
If raising a calve on milk replacer study up a bit on calve diseases, especially scours.
Don't be afraid to medicate a calf, find your local feed store and check out the veterinary supplies.
Don't over do it but don't be afraid to treat it as needed.
The best way to raise a couple of calves would be to buy a dairy cull cow that is bred when she calves raise her calve and another one on her
that 8 months of nursing will yield more growth then any milk replacer diet.
Also be aware that dairy or any calves will require castration and dehorning, for growth and your protection.
P.S. it will be a lot of work.
Yesterday for my brother it was a weigh, worm and sort day for 100 animals, 3 groups, one for finishing 1000 pounds and up, one for continued feeding, and one for breeding replacements
Four people a full half a day moving from one pasture to the barn with the chute, sort into groups, turn out into different pastures..