the critical editions of the Tain by Cecile O'Rahilly are probably \
not exactly what you are looking for. the edition by kinsella is good
in the sense that he seems to have fused the branches of the tradition
and smoothed out inconsistencies. as well, his notes spell out the \
differences in the texts where appropriate. and on top of all that,
his translation and edition is a great read.
in my humble opinion.