Short answer is: for recreational diving and for most of divers it doesn't matter.
Long answer: Many factors affect your diving capabilities. In general; diving is all about two things:
1. air consumption
First you need to know that we don't use air for technical diving, instead we breath various mixtures of air that has higher amount of Oxygen and less nitrogen, sometimes with added helium, which we call this Helix or Trimix, in general it is called Enriched Air Nitrogen (EAN) and is distinguished by gas percentages.
In order to increase your down time, you need to decrease your gas consumption. This is achieved by many ways; for example:
Maintain proper trim (body position and alignment to streamlines) under water to decrease your profile as much as possible, hence, smaller people do better underwater
Practice to know how to breathe (in and out) properly and how to fin without exerting too much energy
Wearing proper gear, and keep your tools tucked to your body to decrease your profile as much as possible, even your head and hands position have a great effect.
While doing a deep dive; deeper than 55m the gas consumption increases too much, adding necessary gear to your diving suit increases the consumption.
The answer: My diving suit and diving gear are tailored to fit me snuggly, to lower my profile as much as possible, all of my gas calculations and dive plans are based on my current gear, hence, adding 2cm here and there to my body measurements and adding 5kgs to my weight will increase my consumption and decrease my down time. Don't underestimate this, 5kg and 2cm at depth of 90m may decrease my downtime by 8 minutes, and will add another 20 minutes for the safety stops and I may need more deco bottles during my ascend to avoid decompression sickness (which is fetal btw!!)
That's why I'm very strict with my measurements
Hope I could explain it clearly