M609,
You're right, I didn't qualify that part of my answer sufficiently, and I can only answer for my type (Global Express, i.e. more power than most). At low levels (below 10,000') 220kts will give the best rate of climb. Slower than this and the rate decreases rapidly. Higher up, 300 kts is required. When I said that we climbed faster at higher speeds, I was referring to certain SIDs with tight turns on departure which limit (for example) to 185kts. A restriction like that reduces performance significantly.