Well, first off you have to read the dog. How old is she and what kind of training, if any does she have now? If I was you I would take her to a trainer in the area and do a lot of studys on both sports. You need someone with exp to see, work and handle the dog. I would also advise taking the dog to the Vet and having her hips looked at first as both flyball and agility can be hell on the legs. What kind of line was she bred out of? Was it a show, pet, or working line? Although she will work no matter what, bepending what line she came out of will make a big differnce on how well she works, depending how far you want to push it.
Beagles are my breed and I have done, weight pulling, tracking, agility, flyball, Sim sports and OB with them. At this time I work most of my beagles in Sim rabbit and fox pinning. All my dogs get fully OB trained on and off lead befor I do much of anything with them "sports" wise, I would recomend OB training your dog, it builds a very stong bond between dog and handler.
No matter what one of the two you diside to go with, just remember to stick with it all the way and dont expect things to happen over night. Truth be told Beagles are not pros at either one of the sports you named as there not bred for either one, but they will do just fine with the right handler and trainer. It really depends on you, give them a good diet and tons of exersize and time. Diet is very important with Beagles as they can be fat dogs, being over weight in these type sports will hurt then, not only there health, but there proforance. Take the time to get your dog on a good food.
Dave.
