C7(b5) Chord on Guitar

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7(b5) is just an alternative notation for a 7(#11) chord. 7(#11) is the recommended notation.

[1]7(b5) has the notes [1] (1), [3] (3), [b5] (b5) and [7] (7).
[1]7(#11) has the notes [1] (1), [3] (3), [#11] (#11) and [7] (7).
[b5] and [#11] are so called enharmonic equivalents and therefore sound the same.

Please also read the description of the [1]7(#11) chord for informations how this accord can be practically applied.

Here is why I would prefer to notate this chord as [1]7(#11) instead of [1]7(b5):
Every chord relates to one or several scales that can be used to write melodies or improvise over that chord. In case of [1]7(b5) respectively [1]7(#11) chord the most common/prefered scale is Mixolydian #11:
[1] Mixolydian #11:
[1] (1) [9] (9) [3] (3) [#11] (#11) [5] (5) [13] (13) [7] (7),
Other scales that might fit in certain situations:
[1] Altered Scale:
[1] (1) [b9] (b9) [#9] (#9) [3] (3) [#11] (#11) [b13] (b13) [7] (7),
[1] Whole Tone Scale:
[1] (1) [9] (9) [3] (3) [#11] (#11) [b13] (b13) [7] (7)
[1] Half-Whole Tone Scale:
[1] (1) [b9] (b9) [#9] (#9) [3] (3) [#11] (#11) [5] (5) [13] (13) [7] (7)

7(#11) leads to the assumption that the relating scale can't have a perfect 4th (11), but may have perfect 5th or b13 with the 5th skipped (that is right!), while 7(b5) might lead to the wrong assumption that the scale might also contain a perfect 4th (11), which would result in a scale with two consecutive half steps: 3-11-b5.

Another important point that speaks for 7(#11): it is great for fast and accurate reading, if certain intervals only come up with certain chord types:
b5 is most likely associated with a diminished or half-diminished chords and therefore a minor 3rd
#11 is usually associated with chords containing a major 3rd: dominant 7th chords like [1]7(#11) and maj7 chords like [1]maj7(#11).

I heard somebody saying that for him 7(b5) means that the b5 is obligatory while #11 means you may add a #11 by choice. That makes no sense for me. There is no parameter in chord symbols that determines a level of obligation or voluntariness. Your musical freedom is much more determined by musical style, instrumentation, arrangement and your personal level and experience.