I don't have first hand knowledge of either injections but I looked up some interesting links about trigger points vs tender points and the treatments for them.
Links below- also explore the sites for more info

http://www.aafp.org/afp/20020215/653.html
http://www.neurologychannel.com/tpi/
http://www.spineuniverse.com/display...ticle1854.html
http://www.medicinenet.com/trigger_p...on/article.htm
http://www.painandwellness.com/spina...ger_point.html
http://www.trigger-point-injections.com/injection.htm

I guess that's enough for now - I get carried away when i start looking for info- LOL

Some of these have nerve block info also.