With large full range speakers is a sub always needed.
Or is it really personal choice?
No it isn't 'necessary' but it can be 'better' if
well integrated with the speakers.
The advantages of using a subwoofer include:
1. A well designed dedicated speaker designed only to produce low frequencies will do so with less distortion than almost all full range speakers.
2. The worst audio anomalies created by your room are in the bass region, with a subwoofer you have far more options to ameliorate the issues with placement or Equalisation.
3. Your speaker amp will be asked to do much less than before so you may experience a much cleaner mid and treble.
4. A well setup good quality sub will be less 'boomy' and may not bother neighbours as much during music, although the deep bass in movies will probably make up for that!
1. It isn't easy to integrate a subwoofer well, to do it right you really need to measure your room using Room EQ Wizard or similar and use it to find the best location and settings for your sub and speakers. This is so often ignored and can make the difference between really good and really terrible bass, even from a good subwoofer. Simple option is to use Audyssey or another auto EQ tool, it is unlikely to be optimum but better than nothing.
2. People quite often like what they are used to. Speakers usually distort a fair bit when producing deep bass and once you are accustomed to this, the clean bass from a good sub often sound 'wrong' or 'missing'. Most people get used to this and appreciate the clean tight sound but some people just don't like it, it may be accurate but not always what everyone likes.
3. The deeper the bass produced the further it will travel so you do need to consider your neighbours. Quite often it can be louder in another room or house than it is in the listening room so you can't always assume if it isn't loud for you they may not be in audio hell.
Personally I couldn't live without a sub or two but I live in a detached house and have the time and inclination to set things up properly, YMMV.
I would call it personal choice.