I would trust Diono or Britax above all others. But, it really depends on the car[s] you plan to install it in. Some seats are finicky to install in certain cars, while others are easy & a perfect fit. Some seats you have to consider the amount of room they take up while rear-facing.
We buy Britax for this reason. Easy install in almost any car! Lasting reputation for safety. Smart simple features, like these little velcro tabs that keep the straps open so you aren't digging under their butt for them when you are trying to buckle them in. Non-rethreading harness, is beyond convenient. They are outgrown by height, before weight...but, by then our kids have always been old enough [6yo] to move into a highback booster [our 8yo is in a Parkway] or 'next stage' harnessed seat [our 5yo is in a Frontier 85]. They also have adorable prints...our littlest is in a Pavilion G3 RF'ing to 40lbs FF'ing to 70lbs
Quoting Jennybananna:" Have you put the foam thing under it? I know it gave me a few extra inches to work with with RF"
The butt cushion? lol, yea, but he's only 4 months, so I don't have to worry about FFing him for quite a while