I'm in doubt when it comes to buying my first foil kite. I've started hydrofoil using Moseshydrofoil vorace. Now I know above kites have some similarities yet diferent in performance and usibility.
If some one can give me some advice what to choose? 
Can't speak for the sonic, but i would say the chrono v2 is a very nice kite to fly, quick and robust. The fone i believe would be a quicker kite for racing but not as robust with regard to the bridal and maybe fabric. For ozone to fone the best comparison would be the R1v2 vs the Diablo. R1 is the race specific foil kite, and seems to be very quick, i think a new Diablo will be out soon. Although if just getting into foiling all would be fine.
I fly a chrono v2 and its still very quick.
What size are you thinking?
11m, 13m, 15m?
hand down chronoV2 is one of the easiest foil kites to fly. feed is very near a inflatable and it loops quicker than any of the other foil kites in that its slightly less high aspect, which is a good thing it seems. Ozone R1v2 the latest ozone race kite has followed the same path now as ChronoV2.ChronoV2 bridle and speed system are hassle free and easy to live with. less tangle too which gives super quick pack up and pack down with the extra deflate vents and zip
I would say for your first foil stay away from the ultra high aspect race foils. Like the sonic, diablo, R1. Consider the next aspect down like the chrono V2, speed 4,5.
If ur buying your first foil kite don't go past a second hand. A lot of the racers keep there gear in good condition and flog them when new gear comes out cheaply..
I have the sonic FR and the Chrono V1. They are both good, But I prefer the sonic but that's just me..
If you have a Vorace I guess you are planning to race, so right now go for Diablo--consensus is they're the highest performing kites*. Otherwise, get a cheap beater Speed3 12 and learn the ropes.
* wait for it . . .
Think the Diablo was the fastest kite. Check the latest results, seems the new R1 has dominated. Although new fone coming..
Flysurfer Sonic 2's are being launched in September. There will be a few quivers of second hand Sonic 1's (9,11,15) available as riders upgrade to the new model. The Speed 5 is our free ride kite which is comparable to the Ozone Chrono v2. Slightly lower aspect than the race kite and much easier to handle and relaunch. Im riding the Speed 5 12m at the moment as an all rounder (surf, TT, foil).
you are spoilt for choice really - I'm sure Fone will have a new Diablo soon too, which means you have 3 different, second generation, race brands to choose from If you want to go that way.
You need not be nervous about the new release race kites.
They have all been designed to be alot more agile and stable compared to previous years, many are going lower aspect in the full race versions with less projection in the tips.
Most racers now on 15m lines or less... You cant do that on a kite thats not agile or easy to fly.
Past 3 weeks iv been running only 10m lines (63cm bar) on my 15m & 17m R1v2. Easiet & best handling foil kite ive flew yet. Alot was learnt from Chronov2 and put into r1v2
Many brands going back to drawing board with the new realease after the domination of the recebt r1v2... Especially downwind they unmatched at this stage but a significant amount.
After repairing a bunch of parafoil kites the Flysurfers are definitely the ones with the best build quality.Performance will not matter than much until you can foil tack and gybe. Also use longer lines in the beginning. 21m is good that way your kite won't be in water as much and you got bigger wind range
