2.3 is gingerbread

and the 2.3.1 , 2.3.2 , 2.3.3 is depend on how many update for the company's phone

2.3.4 mean sony give 4 update to make it bugless and stable

while samsung's

2.3.6 mean it realese 6 update for it

samsung give minor update for its phone while sony give feture like xloud / improve boot time / battery life / panorama and swipe

more number doesnt mean its more latest . It is all depend on the developer . They all still 2.3 tq .