The other day, I was staring at my feet and wondering why my toe nails had not grown as much in a time period when I needed to cut my finger nails twice. So I hit the question on Google.
I found several explanations for this weird disparity. One is the location factor. Fingers being closer to the heart than toes make finger nails closer to the blood pumping source than toe nails. Blood transports oxygen and nutrients that directly contribute towards growth and repair of body cells. Hence, finger nails are physically located closer to the oxygen and nutrients propeller (heart) and more readily approached by their growth contributor (blood). Growth pattern differences follow accordingly.
Another reasoning given for the difference in growth rates of finger nails and toe nails is the trauma debate. Usually, one's fingers experience more movement and activity than the toes. In other words, we can say that fingers typically experience more 'mini-traumas' than their lower limb counterparts. Greater exercise of the fingers instigates more rapid blood circulation between the fingers and the heart, as compared to the blood circulation frequency between the heart and the toe nails. This highlights the subsequent difference in supply of oxygen and nutrients between the nails of the finger nails and the toe nails. Consequently, the growth rate of either nail set differs.
Another popular debate is that the finger nails on the dominant - or the more used hand - are likely to grow faster that finger nails on the other hand. This also follows from the blood circulation frequency reasoning. However, from personal experience, I do not recall witnessing much difference in growth between the finger nails of either of my two hands even though I use my right hand a lot more for most of my single-handed pursuits.
Yet another discussion that I came across presents that nails usually grow faster in warmer weather conditions as compared to nail growth in cooler environments. The reasoning given for this is that warmer fingers and toes would have blood vessels with enlarged vessel diameter due to expansion that would allow for more blood movement and corresponding nutrient exchange. I have not paid attention to notice such peculiar behaviour as of yet.
In light of these enlightening revelations, I would agree that most factors that affect blood circulation seem to influence the growth of nails. And of course, there could be some other parameters (such as genetics, age, medical conditions, etc.) that might also be responsible for different rates of nail growth in the same body.
Scot, "Why Nails on Your Fingers and Toes Grow at Different Rates". Published on January 24, 2013 <http://www.todayifoundout.com/index.php/2013/01/why-finger-and-toenails-grow-at-different-rates/#f4eLhuuKmVWa1MQM.99>
Olivia Gardner, "Do fingernails grow faster than toenails?" Published on April 3, 2011 <http://www-scf.usc.edu/~uscience/nail_growth.html>