Question Britax Marathon or Roundabout?

Ok...I'm torn here. I have a 2.5 year old boy who is in his forward facing britax marathon and we are all pleased with it. I have a 6 month old baby girl who HATES her baby car seat. (graco metrolite travel system) I've decided to go ahead and purchase a convertable car seat BUT which do I get?? I realize the difference in size, price and weight/height limitations. My dilema lies with the vehicle I own. I have a bmw x5 and I remember putting my marathon in the center of our back seat when rear facing because if behind either bucket seats it limits our leg room for me to drive and for my husband or any other for that matter who sits in the passenger seat....and we are pretty tall! The marathon isn't much of an issue when forward facing...just when he wants to kick the back of my seat! lol!! Sooooo, with that being said do I dare take a gamble of purchasing the roundabout in hopes she doesn't outgrow too soon?? It really is a tight fit when that marathon car seat is rear facing. Is there really much of a difference in size?? (i am notorious for purchasing items thinking its a good buy then wind up having to "eat it" or return for something else...I don't want to make the same mistake here!) Please...any input would be greatly appreciated!!

Sorry in advance if i am misinformed but after just researching this myself i found that the roundabout 50 is essentially the same shell as the marathon without the bells and whistles. So if space is an issue rearfacing with a marathon then i would suspect the same would apply with the RA 50.

The Roundabout 50 is essentially the same seat as a Marathon, at least in terms of size. The Roundabout is a smaller shell and will not last as long as the Marathon. You should be able to install your daughter's seat more upright if she has good head control. The seat can be installed anywhere from 45-30 degrees. Installing it more upright will give you more room. So will putting your front seats more upright, if you have them reclined.

What I would do is turn your son's seat rear facing for your daughter, as the Marathon is one of the shorter seats front to back rear facing. Then get your son a new seat to forward face, probably a Nautilus, Frontier, or Generations65.

You are so right. I eliminated the X5 from my car search because even with a pretty upright install on the Marathon, it didn't leave a lot of room.

I didn't own a Radian at the time that I hauled 4 carseats to dealerships all over my area puzzling seats together, but I do own one now and I think knowing the X5 and knowing the Radian that it would puzzle well next to your Marathon in the center seating position.

The only issue would be whether your baby would like the full 45 degree recline.