B12 as methylcobalamin or b12 as cyanocobalamin - which one is safer/better and in what form : pills or sublingual?

No difference: 2 mg oral is supposed to be as good as sub lingual. I usually recommend 1.7 mg SL liquid every week for 2 months then once every 2 weeks thereafter. I recommend maintaining a level of 550 at all times. One should also check folate (folic acid) level and make sure that is OK. If anemic and you are replacing B12 its wise to check for low potassium as correction of the anemia can deplete K+ stores.

Methylcobalamin: Methylcobalamin is the best form of B12. This is the co-enzymated active form that our bodies use.When we take cyanocobalamin or hydroxycobalamin our bodies must first convert these into methylcobalamin, so it's better to take the active form & save your body the trouble of making this conversion. Sublingual may be best but pills have similar absorption if chewed. See http://tinyurl.com/oc8up5z