I've had several Impact Spods and the mechanism on the front has, in general, been miles better than the Spombs I've owned. I must have been lucky.
Both the Impact Spod and the Spombs are inconsistent. Good ones are good and poor ones are useless but I find the Impact Spod is more consistent than the Spomb since the pin problem was fixed.
For general use (filling and chucking) I reckon the Impact Spod is best. However, a decent Spomb is better than the Fox one while a poor Spomb is much, much worse. The retrieve on the Fox is very poor compared to the Spomb and can be quite hard work until you suss out the method for getting them to the top quickly.
I had a couple of DOT Spods imported from Slovenia. These load, fly, and retrieve as good as or better than both the Impact Spod and the Spomb, but the capacity is rubbish.... it holds half what the others do.
I think a real decent Spomb is the best of the lot, but I find you need to buy 3 or 4 to get a real decent one (one that stays closed for every cast yet opens every time when you hit the clip). Pretty much all of the Impact Spods are now half decent (i.e. stay closed on the cast and open every time) so you only need to buy one. If you don't mind spending hours spodding due to capacity issues the DOT Spod is the one - flawless performance, but it takes ages spodding out tiny handfuls a time....
I do think it's time Spomb re-designed their offering - with the lessons learned from the original Spomb and Impact Spod it should be very easy for them to bring out something very consistent that loads, closes, casts, flies, opens and retrieves well.