Having done both I think I can give you some ideas on the plusses and minuses for either idea. Both Jim and Dean make sensible points which raise the question of how commited you are to Florida. Are you interested in more than just a holiday commitment?
At the moment with £ at such a great exchange rate I can understand the attraction of UK residents looking to buy into American assets. Where this could become a problem is the on-going commitments you're are left with either purchase.
DVC has it's "dues" a house has a much larger potential for costs depending on the rental ability. If the £ moves back to it's lower levels of the last 10 years would you be able to fully fund these commitments, don't forget that although many realators will tell you that you'll be able to rent out your house to (help) cover costs few (none) of them will make a firm guaranty that will be the case. My own experience was that the house was costing me between $2-3,000 a year. Granted I was occupying the house for between 6 and 8 weeks a year myself, so it could be argued that my "rental" cost was about $300 a week, but I did have a fair amount of capital tied up. Do be aware that anywhere that's more than 20 minutes drive from WDW ( and baseball city is definately more than that) is going to be more difficult to rent out than somewhere closer to WDW. Villa rental is quite a competative market and to rent out your home will require you to commit a reasonable amount of time to doing so.
Coming back to the point of commitment, IF they would be spending more than 8 weeks of the year in Florida, then I think you can make a reasonable argument for the villa route. Certainly if they are looking at retirement in the near future and would spend say 4-5 months in Florida then certainly a villa is going to be the better option. If however retirement is 10-15 years in the future and they would rely on rentals to help cover their costs I would agree with Jim that a better option would be to buy a house in a decent rental area ( so they are hooked into Florida property values) and they can then decide to move to a different area when they would be spending a lot more time there themselves.
Both ideas have a lot going for them. DVC is a much smaller commitment both financially and emotionally but a villa does offer you the dream of one day spending at least 6 months of the year in Florida once you've retired. I don't think either choice is always better than the other, it is very much dependant of the aspirations and situations of those making the choice.