I have a premium membership at the Autosport site. It's not the membership plus digital subscription, or membership plus digital and print subscription, just the premium membership. Pricing is available there, and I find it worthwhile. I don't think I'm missing much by not getting the print or digital versions of the actual magazine. There is some good analysis on the site if you have premium membership, and it covers just about every kind of racing.
The Motorsport site is nice, too. It seems that Autosport and Motorsport are now merged; I got some email from the editor about this. When I first subscribed to Autosport over a year ago, Motorsport also had a premium membership option, with similar tiers to Autosport. I just happened to go for Autosport, for whatever reason. Now, it seems that Motorsport doesn't offer that any longer. That site seems to offer a fair bit of free goodies, plus subscriptions to the print magazine. Autosport seems to now be their vehicle for the premium online content.
I'm sure either print magazine would have some interesting yearly special issues that one might miss with just a website membership or relying on their free site. But, one never knows. As an aside, that's why I dumped Popular Mechanics. All their useful mechanical information and tips went online, and the magazine became a giant informercial. The print magazine lost the interesting content, which migrated to the free website, not even the premium website.