I just had a thought about the list that MomtoEliEm did (the link above). (Thank you BTW, a very helpful list!)
Maybe if it was divided into categories as to what type of seat it is: convertibles, forward-facing only, combo. This may help your friend make a decision. Also maybe include the retail prices.
What about this layout (I have it saved down so I can easily copy and past into posts when needed)?
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Here is a list I made up earlier showing all the higher weight/height seats available. I am only including those with 17"+ harness height and 41lb+ weight limits. Please note these are US seats. Canada doesn't have all these seats and with some of their seats, they may have different weight limits.
Convertible Seats (installs both rearfacing and forward facing harnessed seat):
Recaro Como/Signo (~$249-$290 depending on model) - top harness height is around 19 inches (Signo is 18 inches, Como is 19 inches) and harnesses up to 70 pounds (5-35lb rearfacing).
Sunshine Kids Radian (~$199-$278 depending on model) - top harness height of 18 inches. Can hold a child up to 65/80 pounds (depending on the model you buy) (5-33lb rearfacing). This seat folds so it can be carried easily (though it is still a heavy seat to carry, especially around the airports). These seats can use the tether rearfacing. This seat is also pretty narrow when compared to other seats so often a good choice when trying to fit multiple seats next to each other in the car. This seat can be tricky to install in some cars so it might be best to try it out in your car prior to buying it.
Evenflo Triumph Advance (~$129) (don't confuse with the original triumph which is actually a very short harnessed seat)- top harness height of 17.5 inches. Can hold a child up to 50 pounds (5-35lb rearfacing).
Compass True Fit (~$179) - top harness height is 17.25 inches. Can hold children up to 65 pounds (5-35lbs rearfacing). This seat has a removable headrest for babies 5-22lbs rearfacing which might make this seat easier to fit into smaller cars rearfacing. The headrest is required forward facing and when rearfacing above 22lbs.
Britax Marathon, Boulevard, Decathlon (~$249-$300 depending on model) - top harness height is 17 inches. Can hold children up to 65 pounds (5-33 pounds rearfacing, though seats manufactured in 2008 should go to 35lb rearfacing). These seats can tether rearfacing.
Cosco Alpha Omega Elite (~$169) - (This recommendation is only on the newer mid-2008 and newer models which have a top harness limit of 50 pounds, not the older models with a 40 pound harness limit and lower top harness height) - top harness height of 17 inches. Can hold children up to 50 pounds (5-35lb rearfacing) in the harness. This seat does convert to a booster when the child outgrows the harness by weight or height, though it doesn't turn into a great fitting booster as it does not position the seatbelt correctly on the child. This seat may not install well in all cars so it is best to try it in the car before buying it to ensure it will fit well.
Youth Seats (installs forward facing with harness):
Britax Regent (~$249) - top harness height is 20 inches. Can hold children from 22-80 pounds. Requires a top tether after 50 pounds (some newer regents require the top tether after 40lbs though). Very big and cannot be taken on an airplane This seat really doesn't work for young children (under 2 who really should be rearfacing anyway) since it is so large.
Safeguard Child Seat (~$429) - harnesses from 22-65 pounds. Top harness slot is 19" high. Very expensive, but a great seat.
SafeGuard Go Child Restraint (~$199) - harnesses from 30-60 pounds. It's harness is a little different and it depends on the seat back. Requires a top tether for installation of seat. Not really the best choice for an everyday seat, but might be good for traveling.
Combination Seats (installs forward facing with harness and then converts to a booster):
Graco Nautilus (~$149) - top harness height of 18.5 inches. Can hold children up to 65 pounds in the harness. This seat is forward facing only and converts from a harnessed seat to a highback booster to a no-back booster. Can use latch to secure the seat while using the seat in booster mode. When used in booster mode, the entire seat base must fit onto the car's seat which may make it incompatible as a booster in some vehicles.
Britax Frontier (~$279) - top harness height of 18.25 inches. Can hold children from 25 to 80 pounds in the harness with a minimum age requirement of 2 years old. This seat is forward facing only and converts from a harnessed seat to a highback booster. Can use latch to secure the seat while using the seat in booster mode.
Cosco Apex 65 (~$129 depending on model) (also referenced as Safety First Apex, Safety First Biltmore and a few other names) - top harness height is at 17.5 inches and can harness from 22-65 pounds. After the child outgrows the harness, the seat does convert to a highback booster. This seat does require a headrest behind the seat so it will not work in cars without headrests or tall seatbacks.
