I was having this same debate a couple of weeks ago! I posted on here to ask people's opinions on preseed versus zestica.
Anyhoo, I had a slight mad moment and ordered preseed, zestica spray and then also bought sasmar conceive plus from boots (yes, I know, bonkers).
Having sampled all three I would say the sasmar is my fave out of the three as it doesn't go as sticky as the preseed but is not as runny as the zestica. It is however very very cold!! (I'm not pregnant though so can't comment on it's effectiveness on that score)
xxSara