Where are the accents, and is this meant to be a polyrhythm?
You have 16 actual notes in your sample notation. That would fit into 4/4 time with the groupings of three forming a polyrhythm. This kind of pattern comes up in rock music...
...something like this seems more common, but follows the same polyrhythm idea...
...actually, that's kind of a ragtime rhythm.
Or like this to carry the polyrhythm over the bar line...
I gave the polyrhythm example using two parts, but you can imply something similar with one part. The important point is to put your brief example into context. If your example changes grouping to threes within an otherwise grouping of fours, you could notate it either with or without time signature changes...
If the main feel is 4/4, then I think the first option is better.
We can't really say what is best without the complete picture of what you are doing. Generally, a meter should pervade through out the whole piece or at least for significant sections. Momentary deviations from the meter will be handled with notation other than a time signature change. For example, for a piece in 3/4, instead of this meter change...
...a tie would be common...
If the feel of groups of 3 and 4 pervades most bars, and you really have an irregular meter, another option is to use additive meter. I think you would use that for your pattern, like this...
...I think technically you are supposed to make the top part of the time signature match the beam groupings using 3
and 2
, but 3+3+3+3+2+2
for the top part seems like overkill.