So I have both options available for baby #2, as I bought an ARC when DS was a few months old and he just decided that big boys sleep in the bed. We're planning to buy a twin bed for the nursery again because it worked so well with DS to have that option - I bedshared in there with him pretty much full time to 6 months, then weaned him into the crib between 6 and 9 months. I just used a rail with him (but now he's using it himself, so we'd have to buy one if I go that way).
Anyone tried both sidecarring and the Arm's Reach and have a preference? The ARC is probably easier to set up and smaller, but the crib is probably more comfortable.
Re: Sidecar crib vs. ARC
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We have the full size ARC attached to our bed. DS slept in it from 2-5 months and it was great. Then he decided he would only go to sleep nursing side lying in our bed, and he is very difficult to transfer. So, for now it's just acting as a "rail" so I don't worry about DS falling off the bed. With summer coming and our crappy air condition I kinda want some space. So I might try the crib side car (he can pull up on the ARC now, which is also something for you to consider....) or mattresses on the floor...
Good luck deciding.
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