People still use v4.1.1 because the attachment system changed for v4.1.5. If you are just starting out you should problebly start with 4.1.1 untill you learn how to edit attachment points. The system for 4.1.5 isn't bad but if you're used to having to edit the attachment points of the payloads, getting them to fit the new system will be time consuming. But neither have any bugs major bugs, it's just different features. Also STSPayloads won't work with 4.1.5 only because of the different attachments. I'm planning on upgrading when I have the time to edit my payloads. I also want to see if I can't get payloads to work. If you're not planning to use payloads go for 4.1.5 but make sure to read the manuals whatever one you choose.
zerofay32