from my personal experience i do feel that digi has improved alot especially their 3g/Hsdpa signal. most of the town and highway digi able to get full bars but no so with my another maxis line where its 2 bars or less.

maxis- noticed that lately they have quite many of blind spots especially at highway and certain areas. like nkve shah alam bound, federal batu tiga, plus south. even gardens hotel conference room maxis has no signal vs digi full bar

digi- speed wise nothing to shout about as i able to get on average 2-4mbps with H+. However digi plans are quite pricey nowadays vs maxis

celcom- so-so only. but 2g coverage is great among the 2 telcos. but in congestion area like mall or traffic jam..sometimes will switch to Edge