I'm quite familiar with the Medallion, though I admit that I've never owned one. I have owned an Ultara and a Horizon, also Evenflo seats.
The Medallion is a fine seat. Installed properly and used right, it will keep your child quite safe. It has that nice cotton-blend Osh Kosh cover.
The down sides are that it has a large base, so it may be difficult to install in your car (and may not - you'll have to try it). It only has two harness slots, and the top one is kind of low, so your child may not fit in it right away (not a problem if you are starting with an infant seat) and may outgrow it well before 40 pounds. Most convertibles have three harness slot positions. The Medallion doesn't really have any of the other special features to recommend it.
In comparison, here are some of the features you get with the Roundabout.
The RA has no-twist straps. No more hassle with trying to keep the straps flat.
The RA has a harness adjuster that works all the time, easily adjusting the harness tighter and looser, even when the seat is installed and the child is in the seat.
The RA meets all US safety standards, but also meets all ECE (European) standards that don't conflict with the US ones.
The RA has eps foam in the head area, which will deform in a crash, unlike just a moulded plastic shell.
The RA tethers rear facing, which gives it quite a bit of added stability, and may help in real world crashes (compared to the ideal situations in crash tests).
The RA comes with a nice pad that is available in a cotton blend fabric. Under the pad is a thick layer of comfort foam that extends all the way from the head area to the knees. Many other convertibles have two pieces of comfort foam, leaving a gap behind the child's lower back, if they have comfort foam at all. Under the comfort foam is the eps foam. Taken together, the seat is quite cushy.
The RA has built in lock off mechanisms if you end up using your seat in an older car (pre-1996) that requires a locking clip.
The RA has three harness slots, from about 10" to about 16", and all are reinforced for forward facing use. In most convertibles, you can only use the top slots when the seat is forward facing.
The RA has a versa tether, which comes from two points at the top of the seat. This also adds some stability.
The RA has some extras, like velcro to keep the harnes out of the way when putting you child in the seat, and a belly pad to protect the child from the buckle, and a nice two-piece harness retainer clip.
The RA also tends to fit quite well in cars. It is at about 90% of the time, from my database (www.carseatdata.org). No seat fits ALL the time, unfortunately, but this one does quite well.
I want to stress again that the Medallion is a fine seat, appears to be comfortable, and crash tests well. Used correctly, it provides a safe ride for a child.
You can probably see, however, that the RA has a number of features that the Medallion doesn't. I would never say that the two seats are about the same. I guess that ARE both convertible carseats, but otherwise....
Some of the differences are about safety features. Like the eps foam, and meeting extra standards in Europe. Some are about ease of use. I find that the RA is more foolproof. It is easier to use it correctly, which may make a big difference, and may not. It depends on who in your family is using the seat, and how detail oriented they are every time you travel.
So only you can decide if the RA is worth the extra cost. But this list should help you see what you'll get from each seat. Both are safe, but they have different features on them.
Do check my database too, and see if there is any information on either of these seats in your car. The best seat in the world isn't so good if it doesn't fit well in your car.
Toby, CPS tech
www.carseatdata.org
[email protected]