I use both 128RC and 700RC2. They're both nice and low-cost, but plenty good. The 128 is the better head, more solid and smooth, but it is twice the weight so the 700 gets more use for me, especially when a lot of walking is involved.
The 128 also has a better locking mechanism. The 700 is safe, but has an odd amount of play in it and you use a set screw to keep it from sliding ( and yet there's not enough slide to balance anything so why have it? Not sure).
Swaros, my Meopta S2, and others I suppose, snap right in to both without requiring a plate. That's handy.
If your scope is not balanced, or if you want to do digiscoping, you might consider going with a head that has a rail, otherwise, I think these are both good birding heads.
Mark