What' s the difference between getting a slackware subscription or ordering the 4 CD set?, besides the cost?

When you order just the CD set, all you get is that the one time. When you do the subscription, every 6 months, or whenever a new version of Slack is released, it just bills your credit card and they ship it to you.

and subscription is little cheaper I think.

It's the cheapest way to get every new release when it comes out. I've been using it since 8.0, and I love it. Not needing to download 4 iso's every six months makes the cost of buying each release worth it. Plus, it's harder to lose the CDs if they're in a pretty jewel case--just in case you need to step back a version or grab some older libraries to make certian programs work.

There is no difference in the product you receive. Same CDs. Same jewel case. Different price. Think of it as the difference between buying off the newstand and buying a subscription to a bi-yearly magazine (if there is such a thing).

Phathead