WojciechMigda: OTOH Spider's meter speed it 3x slower than that of Redwood. I don't know whether the corelation is linear or not
Nope, not really. I believe the benefit of the Redwood's precision clearly outweighs the benefit of the Spider's slower meter. Plus, remember you can slow down Redwood's meter with GI-SD or GI2-S balls, among others.
The best way to proceed is to buy both putters and make the comparison for yourself. I did so, playing rounds alternately with the Redwood and the Spider, and I feel that the Redwood is hands-down the better putter. The price, in this particular instance, says it all. ($6 vs. $4.)
WojciechMigda: maybe it could help if you looked at putting statistics of some players to find those which are close to yours, but their overall average is lower.
The trouble with the stats is that they are often highly misleading. For one thing, none of your practice rounds is included in them; none of your match-play rounds either, I suppose.
What is more, your stats are non-equipment specific, conflating all your results with the various equipment items into a single figure. And, that makes that single figure highly misleading. I've extensively played with all 5 putters in this game, but I have no idea what my stats with any of the 5 putters might be; I can only say I've scored my best rounds when using the Redwood. Neither do the stats show the effect of the ball type you are using, etc. What a great thing it would be, to have equipment-specific stats available, but, unfortunately, that isn't so.