Boosters - P & T vs IGC

Hi

I have a new baby to arrive in the next few months and will need to upgrade my son to a booster.
He is almost 2 and I want to buy one of those boosters that still have the harness and then when they reach (I think) it's 18kgs you remove the harness and use the normal carseat belt and then eventually you remove the head rest and back and end up with a seat booster that lasts through to like 36kg's approx.....
So I see Smiths City have a sale on starting tomorrow.
They have a Phil & Teds Tott XT carseat down from $279 to $223 and a IGC Mothers Choice Raven 3 in 1 down from $179 to $143.
They look the same but I was wondering if anyone had any inside knowledge etc...
Do you just pay more for the name of P & T?

I've also seen a similar one on trade me fwhich people are selling new in the north island for $89.99 plus courier fees.

Any info would help.
Thanks

Hi, we have Edinburgh boosters for daughters (aged 20mths, 4, & 6y), normally $130 at baby factory but pretty much every few months they're on sale for $80. I love them to bits, my 6 year old still uses hers with the full side-impact protection and 5-point harness, and the shoulder harness is still on the 2nd height thingee so she'll fit it for awhile yet. Only problem is taking the actual seat in and out of car as the sash belts sorta weaves through the back of seat. Otherwise fantastic!   

I often wondered what the difference between our ones and the "deluxe" ones were, =). I think those ones go on sale for $120. I just watch the baby factory specials online, saves having to go in, =)