Both a rank taxi and a private transfer will get you from Split Airport to your hotel. The difference is in what you're paying for beyond the drive itself.
Price certainty
A rank taxi runs on a taximeter, so the final fare depends on traffic and route — usually close to the standard rate, but not fixed in advance. A private transfer is quoted and agreed before you travel, so there's no surprise on arrival, and no need to have local currency ready at the curb.
Waiting and matching to your party
Taxis at the rank are allocated in order, which means the car that pulls up might not suit a family of five with beach luggage and a stroller. A private transfer is booked against your actual passenger and suitcase count, so the right vehicle — sedan, van or minibus — is already assigned before you land.
Flight delays
This is where the two options diverge most. A rank taxi has no knowledge of your flight; if you land two hours late, you simply join the queue whenever you arrive. A private transfer service tracks your flight number and adjusts the pickup time automatically, so a delay on the runway doesn't turn into a second wait at arrivals.
When a rank taxi still makes sense
For a solo traveller with one bag and a flexible schedule, a rank taxi is a perfectly reasonable choice — quick, available on demand, and there's no need to plan ahead. The trade-off is simply less certainty, which matters more the larger the group and the later the flight.
The short version
Choose a rank taxi for spontaneity. Choose a private transfer for a fixed price, a matched vehicle, and a driver who already knows if your flight is late.