Agreeing to your statement as for my area only m1 and singtel network are quite stable in my area of living, but not for workplace and as for my workplace singtel and starhub have no issues but m1 has....den again my test was on the prepaid cards and it was like few years ago, but now not sure since i switch my main line on singtel network since no issues on both my work and home.
Everyone has a different usage pattern. i.e., areas frequent. Good that M1/C.Life network works for you so go ahead and enjoy their service. Unfortunately it didn't work for me hence ported out.
Telcos selection is really a personal choice and there is no need to "understand" why there are complaints about a certain Telco; go through all the threads here and one will see complaints against every MNO and MVNOs.