Is this subjective or is there [a] method to this?
This question gives me another occasion to link to the Jacobs School Music Notation Style Guide,, which is a great resource for beginning composers. In particular, here's what they say about notating rhythms:
While there are often multiple ways to beam and group given rhythms, some solutions are easier to read than others. Incorrect rhythmic notation greatly increases the risk of misplayed rhythms, and is one of the “deadliest” errors made by young orchestrators.
Show Me The Beats! It is useful to think of “levels” of metrical hierarchy when notating rhythm. For example, in 4/4 time, events that happen on the half-note level (beats 1 or 3) are one metrical level higher than events on the quarter-note level (beats 2 and 4). One level lower is the eighth-note (events which occur on the “and” of the beat), further divided into the 16th-note level (events which occur on the 2nd or 4th sixteenth note of a quarter-note beat). If a note begins or ends on a level two degrees lower than a beat through which it sustains, the note should be divided, with a tie used to show the higher level beat. Observe the examples below.
In your case, the second note begins on the sixteenth-note level, ends on the eighth-note level, but sustains through the quarter-note level. The third begins on the eighth-note level but sustains through the half-note level. By the above criteria, neither of these are good notation. (The first note, on the other hand, begins on the half-note level and sustains through the eighth-note level, which is just fine.)