Use solid ball for a 2" floater and a hollow ball for a 3" floater.
Will there be any difference in performance?
What is the reason they use hollow balls in some cases and solid in some?
All parties are so far correct in my opinion, exept that the hollow ball valve actually exists, and for cost reasons and weight reasons only: small awith exotic and/or highcost material or larger also with more common material with weight reasons in addition to cost.
If you commercially can buy a solid ball at equal, or slightly different pricelevel I would go for the solid ball.
If the pricelevel are lower for the hollow ball, or the difference totals to a larger sum, I would as stated above check references, certifications and qualifications for the manufacturer of hollow ball and ask for long-term references for the actual applications, to ensure troublefree performance and also analyze cost/lifetime consequences of using the hollow ball.
Some years ago I supplied a series of hollow ball constructed ball-valves  for fairly large ballvalves and higher pressure classes with welded on exotic material overlay on the ball, for offshore use.
This total fabrication process is highly technically demanding, and a limited number of suppliers are able to supply certified top quality.
The end user was fully satisfied with price and performance and bought several times for similar processes over a number of years .

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