I wanted to use just a sling and not a pram, so I bought a very cheap pram, but I find I use them both. Because it's been hot, the sling is not practical for outdoor use, so I've had to use pram, however it will be cooler for you I guess when bubs is here, so a sling is ok.
I find the pram is great for walks and when I pick my daughter up from school, but the sling is good for shopping, when I need my hands!!
xo