Hello. 

Have been using Home Studio 6XL on an older Windows XP machine, worked ok.

recently I got a newer machine, windows 7, i7 processor, huge hard drive, several gigs of RAM (Cant remember how many, not in front of that machine right now)

Home Studio 6XL works ok. I have the Delta 10/10LT soundcard. Everything works like its supposed to, but, if I'm recording and I use the built-in metronome, I get dropouts.

this isnt a dealbreaker, I can get around this, but, I'm wondering

Is Studio 7 better for a Windows 7 machine?

What does Studio 7 have that 6 does not, and, would there be a significant learning curve?

thanks for any replies

If I recall correctly, SHS 7 had less stuff than SHS 6. That was during Cakewalk's 'simplify' period where they removed some features from their programs (Music Creator 5, SHS 7) to make them easier.
As far as working with Win 7, they are about equal in that respect.
If you're looking to upgrade, you should probably get one of the new X1 programs which were designed from the beginning with Win 7 in mind.

Just to add to what Greg wrote,
you cannot purchase a legitimate version of SHS7, unless you find an unopened box lurking in the back corner of a retailers' shelf. Even if you did, I wouldn't bother with it, really. The interface, as Greg noted, was simplified, and I found it extremely clunky compared to SHS6.
I agree that skipping directly to an X1 version is probably your best option.

Just to finalise a note... I bought HS7 XL ...and never used it. HS6 was a far better product in my view. The 7XL version just gave me access to the VST library which came with it. It was probably worth the upgrade price just for.