Having owned both myself you've got a difficult decision to make!
As per all above posts, the torque in the Z makes it less of an effort to get access to all the power and it is a more comfortable place to spend time in over long distances.
With a 10 mile commute each day you won't have an issue with the S2k, and vtec gets addictive especially if you bung a K&N on there. The gearbox is very precise, that's the main difference I noticed with the Z. Even with heel toe etc you just can't get through the box as quickly.
Positives for the Z are engine note (especially with HFC, Y-pipe, exhaust - £1k approx), space, comfort and looks. I had a 1999 S2k with 72k miles and mechanically it still felt like new so if it's a well looked after example that mileage should be ok. Keep an eye on that oil as they tend to go through it fairly quickly if you're using them correctly. Geometry adjustment can be a bitch as the bolts seize up and this can potentially cost £1k+ to sort.
Good luck choosing, don't think there's a 'wrong' decision!