Could anyone tell me how often Navteq and/or Teleatlas (Tom Tom)release new maps please?Also which ones are considered to be the best?

The map makers (navteq tomtom etc) usually release map editions quarterly, as denoted by Q1, Q2 etc, whether GPS companies buy the rights to use each mapset is up to themselves, the big companies like tomtom Garmin etc do while the smaller ones like binatone just buy the rights to one map set and use it across their range, usually with no updates ever available.

To the question what mapset is the better one, that depends on where you are, thus what maps you need and what features you like/prefer. I consider TT/TA the better maps (for where I usually drive around) because they have more detail (esp. house number and industrial areas - things I need for the job very often - while, at least in the past, NT misses that sort of detail). NT maps have the advantage of traffic alerts. When I would like that above detail (around here) I would have to replace my map set. On the other hand we do have traffic signs on the road and as you know, keep your eyes on the road, not on your GPS ;)
Recently I tested the NT set and discovered that locally speed limits (not to be confused with cams) are missing more often. And the final conclusion: I did not get lost.

Just to clarify:

Tom Tom own Teleatlas
Nokia own Navteq.

Having used both sets of maps in the UK, for my type of driving I find the Navteq maps are better, not for the map content which so far I haven't found any difference, but the TTS seems to work better especially in pronouncing words correctly, don't know why this should be, perhaps someone could enlighten me. Each to his own I suppose as the previous answers all have valid points.

exflyboy wrote:Having used both sets of maps in the UK, for my type of driving I find the Navteq maps are better, not for the map content which so far I haven't found any difference, but the TTS seems to work better especially in pronouncing words correctly, don't know why this should be, perhaps someone could enlighten me. Each to his own I suppose as the previous answers all have valid points.

Have you also tried adding the phoneme files form "TTS voices and components?"