Which carseat should I use?

I have a chicco keyfit 30 that we bought without the base (at the time I was stupid and thought I'd only be using it to carry him in because we already had another one)
And I also have a maxi cosi pria 70 with tinyfit.
HERE'S THE PROBLEM:
I know the chicco can be used without the base, but will the hospital cause a problem about it? I don't want to go back and buy a base because they're pretty pricey... BUT
I'm a little iffy about using the maxi cosi because it's a convertible and it doesn't look like the baby would fit comfortably in it, not to mention, I have a 2005 mercury mariner and the backseat is extremely small, so I have to push one of the seat backs to the STRAIGHT upright position, which isn't a big deal but it makes for a pretty uncomfortable ride for me or DH.

So use the convertible carseat
or safe to use the chicco without base?

I would use the Chicco. The base isn't mandatory, it's perfectly legal to just strap it in.

Chicco.
When i brought DD home, i reminded DH a thousand times to bring the carseat that was installed into the travel system (that i had been testing earlier that day) and the base out of her bedroom closet.
Well he turns up with the carseat. No base. I about had a cow. But, my nurse reassured me that the base isn't mandatory, and she'd be fine on the ten minute ride home.
GL  

<blockquote><b>Quoting pilot Jess:</b>" I would use the Chicco. The base isn't mandatory, it's perfectly legal to just strap it in."</blockquote>




 

My hospital didn't even check to see if there was a base or if it was strapped in properly. They DID have me bring the seat in both times, however, for the carseat test

the only thing my hospital looked at was that we had a carseat and the straps were TIGHT! they didn't go to the car to see if we even buckled it in. lol

Thank you ladies! I'll throw the maxi in the back just incase something goes wrong but looks like chicco it is!

Quoting ☼ Mª mª:" I have a chicco keyfit 30 that we bought without the base (at the time I was stupid and thought I'd only ... [snip!] ... it makes for a pretty uncomfortable ride for me or DH. So use the convertible carseat or safe to use the chicco without base?"

I'm assuming the Chicco you bought used, since they are always sold with the base when new! In that case, I would use the Maxi Cosi Pria...unless that was also purchased used, in which case I wouldn't use either.

Quoting .chele.:" I'm assuming the Chicco you bought used, since they are always sold with the base when new! In that ... [snip!] ... new! In that case, I would use the Maxi Cosi Pria...unless that was also purchased used, in which case I wouldn't use either."

I actually bought it from wally world! It just came with the carrier and instruction manual. They had the bases right beside them and then beside that they had the strollers. I didn't grab the "travel pack" or even just the base at the time because I didn't think I would actually be using it in the car. It was either buy the set or pay close to 100$ for the base and 200$ for the seat, and I already had a stroller and carseat, so I opted for just the seat! The Maxi cosi was ordered from the actual website, son of a bitch took 7 weeks to get here!