It depends on the size of your round but the honest truth is that none of them are effective by themselves. They can be helpful in constructing the total round, but would almost never be able to raise 100% of the round, assuming you're talking about a true seed round of at least $750k.
If you feel you're ready to raise a seed round, there are a handful of seed stage funds that like to lead deals. I have just answered another Clarity question where I list them: https://clarity.fm/a/6503
There are then a number of great funds who will follow in smaller check sizes (average $250k-$500k) behind those lead orders.
These services you mention are best to "fill" a round, when you're looking for extra money, but can't be relied upon to "form" a round. Hope this helps!
