I have the britax poplar s and love it. It’s pretty easy to install and my boy seems comfy in it. It has high rear facing limits which was really important to me.
All in one covers more modes than just simple rear and forward facing modes
All in one offers a lot of modes, but the flip side is that just because it can do a lot of things.... Doesn't mean it does all of them well ( Jack of all trades, master of none, sort of thing if you're familiar with that analogy)
a convertible car seat goes from rear facing & front facing while the all-in-one does both of them as well as a booster seat! they both would work, just depends if you wanted to get the option that can be transformed into a booster seat later on!