Best current untethered jailbreak/ unlock for 3GS / 4.21 / 5.15.04?
Just got a used iPhone 3GS and erased all pre-existing content by using the iPhone's Settings/ General/ Reset menu and then hooking it up to iTunes and having iTunes recognize it as a new iPhone.
Now I want to jailbreak it and unlock it so it can be used with T-mobile instead of ATT.
From what I am reading in various places on the web, I DO NOT WANT to upgrade the Modem Firmware from its present 5.15.04 to Apple's current 6.15 because it could have negative consequences in the future (but I don't understand the details of that.)
It seems that if I use RedSNow that problematic change of firmware would occur but if I use GreenPoison ( greenpois0n RC6.1 (win) it won't so it would be the preferable tool to use. ??
I am posting because with everything constantly changing in the jailbreak and unlock world from both Apple and jailbreak / unlock tools, it is hard to find what the current truths are.
Would appreciate current advise on the best current untethered jailbreak/ unlock for 3GS / 4.21 / 5.15.04.
I would also like to know if I can or should update the iOS from 4.21 to ... whatever ... either during or after this jailbreal / unlock process and if so how I go about that.
Thnx in advance,
NOTE: My first choice would be to do this from an XP PC but I can use an iMac if necessary ...