Basically anything that fits your budget, your child, your car, and that you will use correctly every single time.
They're all as safe as the next when used properly.
However, having said that Evenflos and Graco convertibles are not favorites, they have short shells and low RFing weights (only 30 pounds).
The Cosco Scenera is recommended often because it's a good RFing seat (any Cosco/Eddie Bauer/Safety 1st convertible seat is good RFing because of the weight limit) since it RFs to 35 pounds. Highest on the US market. It's $40 or so. It only FFs to 40 pounds, though, and a lot of kids outgrow it by height before 40 pounds anyway. So you'll need another convertible. But as it is $40 it's not like you're throwing away an expensive seat.
The other ones that are highly recommended are the higher weight Britaxes (Marathon/Decathalon/Boulevard). They RF to 33 pounds, have a RFing tether, are very comfortable and padded, easy to use, have straps that don't twist, have high slots, easy to install and most kids fit in them wonderfully. They're likely to be outgrown by height rather than weight (since they all FF to 65 pounds) but even so it's likely you'll get five or so years out of it, maybe more. Which of the three Britax convertibles you get depends on your budget, which features you like best, and maybe even just which cover you like best. They're all built on the same shell, so they're all very similar. The Boulevard has true side impact protection with wings and a harness that you adjust with a knob rather than rethreading. The Decathalon has infant padding, a toddler pillow, different FFing lock offs, no black bars for the LATCH anchors, and a push button harness release.
HTH
Wendy