Pretty much true, depends on how you measure performance between aircraft. The 60-series has good overall climb performance and will maintain its climb rate into the high 30,0 and low 40,0 Flight Levels where the 20-series had a tendency to SCREAM through the lower levels up to about FL250 then you had to watch your airspeed carefully to keep a decent climb rate (higher airspeed = L/D Max = best rate of climb).
My record for climb is in a Lear 24D with the F mods coming out of IAD one night rigged for freight (most of our interior removed) but with no return freight (holiday weekend), wings and half tips of fuel. We took off RWY 19 straight-out with a climb clearance all the way to FL 410 and crossed the airport boundry at 10,000 - the VSI was pegged, have no way to know what our climb rate was but it was so little forward movement that departure radar couldn't see us for the first minute or two we were talking to them. We made it to FL 41,0 in 9 minutes and 22 seconds, average climb rate to altitude: right around 4,500 fpm.
A LR 60 couldn't keep up with a 24 in the first 20,000 feet, but would probably outclimb it in the 2nd 20,000 feet, those high bypass fans kick out a lot of power in the upper altitude range. Most of the Lears have a wing root problem past Mach .81, that is, they induce a LOT of drag at the wing root. There's actually a new mod for the 20- and especially the 30-series wings that is irreverantly referred to as the "bat wing" project (looks like a bat wing at the wing root) that is supposed to help with that problem and require less power to keep Mach .80 at cruise which should save fuel.
Should be interesting to see what happens and if it would be lucrative enough to retrofit the 20- and 30- series aircraft for RVSM... Been watching the prices on those aircraft drop by 60% over the last 5 years because of upcoming RVSM problems. Someone could make a LOT of money if they could come up with a cost-effective RVSM upgrade, combine it with that wing root to save fuel, and buy up all the 30-series out there and retrofit them. Would cost about half the going purchase price of a 31a and still have longer legs...