We were having exactly the same conversation last night, and we still haven decided what to do for the best
to be fair we've probably got another 4 months before Niamh will be big enough for the 9mth to 4yr seat, I sat her in Oscars last night, there is no way she is big enough to sit in one yet, and it's a nightmare I hate her facing the back, although on the plus side, she and Oscar can see each other easier that way than they would if they were both forward facing! We've been looking at this one, halfords have a sale online and in store (online is cheaper)
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_763111_langId_-1_categoryId_165554
Mainly because it matches the one we have for Oscar, I think we will let niamh have the new seat, I have a bit of a thing about Niamh having everything passed down from Oscar and him getting the new things all the time, probably because I always had my older bro's cast off's and never had anything new myself untill I was 12 and I got my very own brand new bike, after having 3 of Dan's old ones!
Also, I can't remember the last time I took Niamh out of the car in
her car seat, we just leave it in the car and take her in and out same
as we do with Oscar, we have a base though so no messing about with
seat-belts, but I think it is much safer to have them rear facing for as
long as you possibly can, in some european conutries they have to be
rear facing unitl age 4, apperently until this age they can suffer badly
in accidents if they are forward facing.
I'd wait for a while yet if you can hun
xx