hmm, okay. But how can that be a problem?
You can't retain the original layer break position.
I prefer DVD-R over DVD+R, because DVD-R runs in more DVD players
No. That's complete nonsense. Once you've changed booktype to "dvd-rom", dvd+r plays on all players.
The only problems that arise in compatibility with playback at that point are typically due to a lower reflectivity depending on the reflective layer used in the blank disc.
In fact, having booktype changed to "dvd-rom" can help to ensure compatibility, especially if players are checking for media type (used to be a common check with some game protections).
I don't buy dvd-r.
How can I get CMC stuff here in Europe?
You may already if your Verbatim is made in Taiwan. You would need batch codes/serial codes (often found printed on the inner plastic hub of the blank disc). This thread is old, but it gives you an idea of what to look for:
http://club.cdfreaks.com/f33/identifying-prodisc-cmc-verbatim-16x-175056/
How can the quality of a DVD blank be measured?
Longevity testing (exposure to different environments including heat and humidity)
and
PI/PO/jitter testing (over a wide variety of burners) is common online
and
CATS testing
I also like looking at C't test results (typically shows how various burners do with certain types of blank media):
http://www.cdrlabs.com/forums/test-results-burners-t13405.html
So, having MCC blanks is a good thing?
Well a lot of companies that produce blanks for Verbatim use the MCC media code. So MCC, in of itself, may not mean much. MCC and being made in Singapore are good things.
Well, is "Datalife Plus" something US like?
It has been mostly phased out in Europe. Datalife Plus is still found in the U.S. and Canada.
in terms of DVD blanks I can only buy "Extra Protection" and "AZO", where AZO is the better quality.
That's misleading. In the past Super Azo may have been better. That's a tough call lately. "Extra Protection" refers to the top layer of the disc. It's a harder top coating, which offers more scratch resistance and protection. These discs are produced by various manufacturers, and so, you may get different results. "Azo Crystal" is even better than "Extra Protection". "Crystal" is even more resistant. Keep in mind that some "Extra Protection" discs that were made in Japan by Taiyo Yuden were excellent.
Typically Verbatim discs made in Japan are produced by Taiyo Yuden.