Looking for recommendations for multiple (convertible?) car seats

Our first daughter (and only child, so no previous experience here...) is about to outgrow her infant car seat, so we're needing recommendations on what to get next. Problem is, she pretty routinely rides in 3 different cars -- both of ours, and my sister's, who watches her a few days a week.

Here's the relevant info:
Daughter: Almost 11 months old, 29", 21lb.
2013 Nissan Leaf: Primary car for short local drives.
2003 Subaru Outback: Used for medium-long trips, also frequently used for local drives.
2015 Dodge Caravan: Sister's vehicle, she'll only be in there for really short local drives.

I think that we'd like to not spend too much on the seat for my sister's car -- don't need many bells and whistles on that one, just safety. Would be nice if it could switch from rear-facing to forward-facing.

Don't really know what features we should be looking at for the other two. Would like to keep overall costs somewhat reasonable, but we're not constrained by a tight budget.

Thanks in advance! Let me know if there's any more info that would help.

I always recommend that people check out the reviews and recommendations at carseatblog.com. Here is a link to the recommended convertible seats. The thing to keep in mind is that all manufacturers will try to convince you that their seat is the safest and we just don't have enough data to tell who is right. All seats must pass federal testing and many manufacturers do tests beyond what is required, but unless two manufacturers did an identical extra test and told us the results (which they don't), we wouldn't have a way to compare their relative safety. That being said, if a particular safety feature seems to you to be a really good idea, and if you have the budget for the seat, well then you might as well spring for it.

Proper use is really the only thing that we 100% know makes a difference in safety. So whatever you buy, make sure that everyone who uses the seat knows how to use it correctly. Many seats have ease-of-use features that make proper use more likely. For instance, Britax ClickTight seats and Nuna Rava have very easy seat belt installations.

In the end every seats has its pros and cons. Take a look at the carseatblog reviews and, if possible, check out floor models in stores like Babies R Us, Buy Buy Baby, specialty baby stores, and even Target/Walmart, and see what you think. If you have specific questions about specific seats, then let us know!

For your sister's car, you might want to look at this comparison of convertibles under $100.

I would avoid the Guide 65 in the Grand Caravan as I've seen some install issues with it. Other than that there are some great budget choices available.

Thanks to both of you for the suggestions, tips, and links. Here's the current plan, subject to change. Thoughts?

Cosco APT 50 for my sister's Caravan
Evenflo SureRide DLX for the Leaf
Maxi-Cosi Pria 85 for the Subaru