actually hindi sila halos same price, ip4 is about 8k-10k pa yung factory unlocked same goes to the lock variant with sim unlocker while on the other hand s3 mini just plays around 5k-6.6k depending on its condition, and if you're lucky enough you could find a seller that just sells it for 4k.
about sa pano malaman authentic madami paraan, pero the best is Odin Mode kase kase halos di ito magaya ng clone, the way to do it, just turn off the phone then hold this 3 button power+home+volume down, lalabas dun download mode. then another way is to get it's imei and check sa website, to test for the functionality use LCD test, it's also 1 way to tell if the phone is authentic the downside mediyo nagaya na ito ng mga clone. just dial this *#0*# and lalabas agad yun LCD Test puwede mo na dun itry halos lahat, like touchscreen, sound, earpiece pati mga sensors. always check for the battery kung bloated and kung sa tao ka bibili sabihin mo test all you want from meetup, laruin mo, pag nilalaro mo dapat atleast 1% per 3-5 minutes ang battery consumption, pag pansin mo at sobra kumain ng battery then there's something wrong, always check for the seal, if it's sold brandnew in the philippines check for the NTC Seal and samsung seal, pag sa ibang bansa nabili then check for samsung seal, madali makita mga seal na yan, NTC Seal just remove the battery makikita mo na toh, for the samsung seal its always located kung saan may screw hole and may tatak na samsung. if wala or isa sa mga yan is tampered na, then most probably nabuksan na ang unit, minsan idadahilan sa iyo pinalitan ang housing kahit nirepair naman ang hardwares nito kaya ingat. testingan mo lang ng testingan dahil may right ka naman dun at buyer ka.
sa tanong mo naman na kung worht it, yeah, it is, for a small 4inch phone, it can play HD Games and napakarami available na Custom Rom, been playing with my s3 mini since i got it and it's running android 4.4.4(Latest) and it's keeping up. if im going to choose between ios and android os, i'll go for android, more customization = more fun and more control over the phone. you know how apple works, it's a money pit. not being bias.
wow ang dame kong natutunan sa inyo idol pag nakabili na po ako idol paturo ako ng update sa 4.4.4 (custom rom po ba ito) thanks po.