105 is a much stronger compound than the SIP polish. It works faster, dusts more, removes more defects, and leaves a hazier finish.
SIP is sometimes used to follow up 105 to further refine the finish leaving you with only one step after SIP to go, namely 106.
order of operations: depending on clear coat (read vertically)
Something like a surfbuf pad and 105 will leave a super jacked up finish, but it clears up relatively easy. YOU HAVE TO # STEP ANY PAINT IF USING SURBUF IMO. Orange and 105, you might be able to get through and have a suitable finish with 203 and a white or hydrotec tangering pad, or even 106 and a black pad on some paints.
SIP and 106, thats a killer two step combination though, which reminds me I need to get a new bottle filled with SIP ASAP.