Shore Excursion details severely limited

We are perusing the shore excursions for our Italy and Greece

cruise this October.

The total length of the tour is stated, but there is no information

on departure time(s) availability. Also, there are very similar tours listed

for destinations without any differentiating information explaining the

variable pricing.

Here are some examples from the Naples port:

1. Taste of Sorrento and Pompeii- Small Group; 8 hours, $219.00 (HOW SMALL?)

2. Celebrity Priority Access Taste of Sorrento and Pompeii; 8 hours, $139.00

3. Pompeii On Your Own Transfer- 3.5 hours, $39.00

4. Explorations of Pompeii- Small Group; 3.5 hours, $99.00

Please define Priority Access and Small Group. Is the "On Your Own Transfer" just providing transportation to the site? Pompeii is our priority and the smaller the group, the better. So, would it be in our best interest to just do the Celebrity transfer and hire a tour guide to meet us there?

When on a different cruise line, the shore excursion research was more detailed and we could select the time of the tour. This would be helpful.

P.S. We DO NOT enjoy going to the "shopping" areas designated by the cruise line so we can buy mass produced souvenirs or those made in China.

Thanks!