How Many Markers to Test and By Which Company?

Regarding the latter I don't think it's my place to advocate one company above another but there are certain aspects participants need to take into account. When two individuals test the goal is to compare marker to marker. The more exact a match  the closer a proposed relationship. The more markers that mismatch, the less chance of a relationship.

NB:

Factors that have to be considered when comparing results.

To-date participants have tested with http://www.familytreedna.com/ , http://www.relativegenetics.com/relativegenetics/index.jsp

 & the Sorenson Project at http://smgf.org/

FamilyTreeDNA *these are group rates which can be purchased with the following link:

http://www.ftdna.com/surname_join.asp?code=D96957

RelativeGenetics SMGF
Y-DNA 12 markers at ($99) Y-DNA 18 markers ($95) Participants are not given any results but these are added to the public database twice a year.
Y-DNA 25 markers at ($148) Y-DNA 26 markers ($155) [of which only 21 are comparable to FTDNA's 25 marker test]* 39 markers can be extracted but it's a laborious process. [classified as 36].
Y-DNA 37 markers at ($189) Y-DNA 43 markers ($195) [of which only 32 are comparable to FTDNA's 37 marker test]* All 39(36)  can be compared to 39 of RG's  markers or 34 of FTDNA's.
Y-DNA 67 markers at ($269)* this test should prove particularly useful for determining degrees of relationship with precision and subgroups within families. Combining this with the Sorenson project would give 76 markers. * the 5 marker's tested by FTDNA but not by RG can be obtained from http://www.dna-fingerprint.com/ Participation in the Sorenson Project entitles individuals to a $60 coupon off the 26 marker test with RG.

There are pro's & cons of testing with any of the above companies. There are also other companies with which individuals may choose to test. The following link describes, and lists, these in more detail:

http://freepages.genealogy.rootsweb.com/~bonsteinandgilpin/dna/ydnaco.htm