I will be in Sicily. I am definitly visiting Agrigento's "Valley of the Temples".
BUT, when i am near Trapani and driving TOO Agrigento i might have time for Segesta or Selinunte or both. If i can only take in one, which do you prefer.
Thanks in Advance.

Impossible to compare. Selinunte is a little more along the way to Agrigento, in terms of geography.

That is not really an issue for me since i will have a car and can drive wherever i want. Which one is more WORTH the visit. If you had to pick one.

I think Selinute is "more" worth a visit than Segesta - BUT, since you are planning to visit Agrigento, I would recommend that if you have to pick one that you visit Segesta. In my opinion, Agrigento and Selinute are more similar in layout than Agrigento and Segesta. At Segesta, the setting for the amphitheater is unlike anything at Selinute or Agrigento.

There is much more "archeology" to see at Selinunte, many more ruins. A visit to Selinunte will take longer (several hours) than to Segesta (one hour).

But Segesta has a more beautiful Greek Temple, as well as a Greek Theatre up the hill. There is no theatre at Selinunte, but there is a necropolis and the ruins of nine temples.

Maybe not impossible to compare, but certainly difficult. Selinunte has more ruins than Segesta, but most are fallen stone (including an entire city.) There are some reconstructed buildings. Segesta has two main attractions: the temple and the theatre. But both are incredibly well-preserved. We did Agrigento, Selinunte and Segesta all on the same trip and I can't say that one is unquestionably "better" than the others. Agrigento is bigger and takes more time to see. It is also much more crowded and people are generally not allowed to climb on the ruins. Segesta and Selinunte are more laid back.

BOTH!

Thank You ALL!
I think I am going to try to do both. I am spending the night in Erice. Plan on fooling around there for the morning then do Selinunte and Segesta on the way down to Agrigento. I will tour "The Valley of Temples" the following morning.
I just wanted to know because if i spend TOO much time in Erice and leave later than I will have to choose which to do. I am sure I will be happy with either/or.

Don't spend too much time in Erice: it's not worth it. Two or three hours AT MOST. One hour in Segesta is fine, as are three or four in Selinunte.

I agree with GAC about Erice. It is nice, but definitely not worth spending the night there. On top of being expensive, there is nothing to do there at night (and you are basically stuck there because you don't want to drive down and back up the mountain at night. Spend an afternoon in Erice, then spend the night somewhere convenient to either Selinunte or Segesta. Get an early start, and you should be able to see both (although I think Segesta deserves more than an hour.)

thanks for the advice.
i think that is what i will be doing. we will be arriving in palermo in the afternoon and then i am driving counter clockwise around the island actually visiting palermo last. i plan on flyng in, grabbing a car and getting to erice (hopefully before sundown) then starting my vaca from there the next morning.i picked it because it was sorta neat and sorta on the way. i will eventually be making more night stops in agrigento and taormina (as a base for the east) and eventually back to palermo.
i think it is totally feasable to wake up in erice, drive to Sel. & Seg. and make it to agrigento in one day. i will wait to see the temples there the next morning.
How long do you take to visit "the Valley of Temples"?

GAC- you seem to be a Super expert at anything Italian.
I plan on visiting Mt Etna also. Do you prefer a tour or do you think we will see enuff driving up ourselves?

Valley of the Temples: several hours. Add two hours for the Archeological Museum.

Mt. Etna: you can do the drive yourself.

you have been a huge help.
ever considered starting a vacation company?
i can be your first client

I'm honored. Thanks for the compliment. I place my postings with the aim of helping travellers enjoy Italy more, and hopefully save some money in the process.