I have several of those depending on how full, intense you want it:
1. The Ryder
is a universal one and you can't do anything wrong with it
2. The Gapers Organic
is I guess the best inflatable by far. The advantage is that you can increase and decrease the size while you are at it.
3. The Pfun plug
is extremely good for for the P-Spot especially in the missionary position
Hit's it very well.