mamaz0n, I only have experience of WW, but know 2 or 3 people who've done SW, so my knowledge of how well SW works is limited to just their feedback, IYSWIM.
WW new system assigns ProPoints (PP) values to foods based on how much protein, carbs, total fat and fibre are in things. The reason they changed it is because our bodies use different amounts of energy to digest different foods, so the net calories AFTER digestion depend on how hard your body works to get it through you.
Protein is harder to digest than carbs, so proteins tend to have slightly lower PP value. The example they give in the meetings is two breakfasts: two crumpets with marg and jam, and a fry up with egg, lean grilled bacon, tomatoes, and mushrooms. Both 300 cals, both would have been 6 points on the old WW method.
Now though, the fry up is 7PP and the crumpets are 9PP (because the fry up is heavy on protein).
The other big difference between old and new WW is that now you get daily PP which you use or lose (depending on weight, height, age, etc), plus 49 weekly PP which you can use to support RL activities for which you may need a buffer (eg, going for coffee with mate, just got to have that muffin, or you've maxed out on your dailies, but you fancy a glass of wine with dinner). You can use your weeklies to top up your dailies each day, or all in one day even if you're going out for a slap up meal.
I lost 2st on the old WW system, and on the new PP system, I've lost 12lbs since mid-Jan (with about 4 weeks intermittently when I've been away/ill so haven't tracked)
All I know about SW is that it hasn't really worked for my friends, and they all gave up after a few months as the weight loss was just not good enough. One of them said they found it a really strange approach to weight loss and didn't see any logic as to why it would/should work. But that's only them, I'm sure it's worked for lots of others!