1. Check if both tripod max load meet your need (your equipment). Go for the one that meet your need (duh!)
2. Is the weight of tripod concern you? Just imagine yourself carrying this tripod +ballhead+all your equipment all day long. If yes, go for the one that is lighter
3. Is the length of the tripod folded concern you? If yes, go for the one that is shorter. If not, go for the one that is closer to your eye level (fully expanded) without having to extend its center column.
I feel that number 1 is the most important, number 2 and 3 is a trade off (you can't get both) -- carbon fiber anyone ?
Slik Pro 500 DX is heavy. I definitely carry it around with a strap. You might not feel it when going for short distances, but if walking for a full day or going for tours, every kilogram counts and compactness is also an important factor.
It all depends what you want. It's a trade off. Better, Lighter, Cheaper--pick any two
Actually, 500dx and 400dx are about the same weight ...... hehehehe.... but then for travelling, I will use 400dx, but for stationary item I will use 500dx as 400dx is less bulky, 500dx is longer and the legs are thicker
What's the problem there? As I mentioned 500DX is bulkier but able to carry heavier weight, even though the weight of 500DX is similer to 400Dx. 400DX is more vesatile. When I go overseas for tour, I will bring along the 400DX and not the 500DX. But when I am talking still life pictures or macro, I would rely on 500DX more as it is more stable.