I think I've read that Famitsu had a better coverage than Media-Create too.

That is, you can't trust one more than the other. Each one of these trackers are forced to a certain extent to approximate the uncovered retailers (through differents mathematical algorithms). That's where the errors come from. Sometimes, Famitsu will estimate this part better than Media-Create, and sometimes it will be the opposite, you can't really say.

So you have to relativise the numbers that you read. If Famitsu says Game X has sold 12,500 units and Media-Create says 13,644 units, you must think : Game X has sold approximatively between 12,000 and 14,000 units, and make your personnal analysis based on this bracket.

This, is true for the NPD, GFK, VGChartz and Chart-Track too. Don't think their numbers are exact.

I don't know if that helps you.

They're both very accurate. They will both be off a bit at times, but they're both more accurate than the NPD I would believe.

Either one you go with is completely fine, as they're almost always within 10% of each other on weeklies and 5% on LTs.

If you're going to write an article, stick to the numbers that sound more credible (ie, don't use the leaked numbers from MC, use the official from Enterbain, or vise versa, but I guess that is obvious)

Fun fact:
Famitsu started to track sales using information from only three retailers in Tokio and two in Osaka ( 1986 ).

media create takes always more time.

from what i seen they are generally more accurate

 Any proof to back this up?

Some hard data about Famitsu :

Drawing from our extensive network within the Japanese game market, our sources include:

3,200 participating retail stores in Japan

31,000 other franchise and convenience stores in Japan

http://www.enterbrain.co.jp/en/c_outline/mark.html

And, what about dengeki? The best tracker could be the one which use all the informations found by the three tracker. But, he don't exist, so we make with what we have. The discrepencies between the three tracker can be big, which suggest the three tracker have a bad coverage, in comparison to chart track (90 % of UK market).

Some hard data about MediaCreate:

Characteristics of the two data sources and a wealth of high coverage

Retail POS data are based. Coverage of data sources, roughly 57%, and cover a wide range of businesses. In addition, the availability of pre-shipment and digestive conditions, trends and data around pre-owned, and used as a complementary qualitative information from interviews with the store.

http://translate.google.com/translate?prev=_t&hl=it&ie=UTF-8&u=http%3A%2F%2Fwww.m-create.com%2Fcompany%2F&sl=ja&tl=en&history_state0=

Personally I use Famitsu for historic data and MediaCreate for current trends ( Nintendo uses always MediaCreate ).

EDIT: Oh I forgot MediaWork's Dengeki ... well who cares.