MIAMI — FOR more than a decade, Robert and Tina Simon lived in a Miami town house enjoying the city's cosmopolitan pleasures from Little Havana to Key Biscayne. But next week, the Simons will move with their four-year-old son to a two-story house in central Florida, lured by such urban untouchables as a backyard and basement. ''Many of our friends have already done what we're doing,'' says Mr. Simon, a banker. ''You can get a much bigger home with more land than what we're paying for here. The schools are also considered to be much better than in Miami.'' The Simons are part of a significant economic and geopolitical shift in one of the nation's fastest growing states. Already a magnet for tourists from around the globe with attractions like Walt Disney World, central Florida is now increasingly a mecca for businesses and residents from the southern part of the state. ''Orlando has many pull factors that are attracting south Floridians - less crime, a slower pace of life, and great expansion possibilities for business,'' says Joe Feagin, a demographic researcher at the University of Florida in Gainesville, Fla. Though Miami continues to successfully attract residents and companies from South America, the city is experiencing ''white flight.'' Between 1982 and 1992, the proportion of the non-Hispanic white voters in Dade County dropped from 80 to 40 percent, Mr. Feagin says. During the same period, Hispanic voter turnout doubled, rising to 40 percent of the total. While some former Miami residents complain of crime and an expanding Spanish-language culture, Feagin says the white exodus is prompted in part by ''the newness of Orange County and that is why families are deciding to pick up and move there.'' Big business is following the trail up the Florida Turnpike to Orlando. Los Angeles-based MCA Inc. announced plans late last month, to spend at least $2 billion to turn the company's Universal Studios Florida theme park in Orlando into a ''major resort destination.'' The expansion - which will quadruple the size of the park from 200 acres to 800 - will add another theme park, a 5,000-seat movie complex, a new golf course, and more shops and restaurants. ''The success of Universal Studios Florida, coupled with the continued growth of worldwide visitors to the Orlando market, have enabled us to make this investment with great confidence,'' says Ron Bension, chairman and chief executive of MCA Recreation Services. City leaders have worked tirelessly with private industry for decades to create a ''business-friendly'' environment in Orlando. The state has no personal income tax, and while much of central Florida has yet to be developed, it sports an infrastructure that could accommodate further expansion. Disney World - with its 27,000 acres - and Universal Studios and SeaWorld all see growth possibilities. ''Location has much to do with Orlando's success,'' says Rick Tesch, president of Orlando's Economic Development Commission. ''Metro Orlando is situated at the approximate geographic center of the state, and development can still expand outward.'' Metro Miami, with more than 2 million people, still dwarfs Metro Orlando. But last year 17,000 people took up residence in Orange County, pushing the population to nearly 760,000 - more than double the figure of 20 years ago. THE competition between central and south Florida extends to the tourism industry as well. Central Florida has always been a popular destination because of the theme parks located in Orlando and the Space Center in nearby Cape Canaveral. And Mickey Mouse is bringing them in faster than ever. In 1994, nearly 34 million people came to Orlando for business or recreation - about 2 percent more than in 1993. Meanwhile, Miami has seen its number of international visitors drop over the past two years. ''Much of that downward trend has to do with the negative publicity south Florida has received over its perceived crime problem,'' Feagin says. ''The numerous attacks against foreign tourists two years ago only reinforced that image.'' And Miami is fighting an uphill battle in the race for tourists. While the Greater Miami Visitor and Convention Bureau has an annual advertising budget of $1.4 million, Disney World alone spends more than $100 million to get its message of ''fun in the sun'' on television. Those commercials appear to be doing their job - even beachgoers are trading south Florida for Orlando. ''Eighty percent of all Europeans and 70 percent of all South Americans are visiting both destinations,'' says Bill Anderson, at the Miami visitors bureau. While tour operators and demographic experts acknowledge that ''hot'' places to vacation and live are cyclical, Orlando sees its popularity as cast more in cement than sand. ''When the Orlando Magic basketball team began playing here, that convinced this community and the rest of the country that Orlando was a major player,'' says Linda Buckley, spokeswoman for Universal Studios Florida. ''And the fact that other professional sports teams still want to come here proves that Orlando's potential has not yet peaked.''