There is an advantage in having a smaller total supply, the range proofs get smaller (513 bits for each bit of the total coin supply). Since Bitcoin's supply is ~2^50.9, a total supply between 2^40 and 2^50 is desirable.
The distribution curve is difficult to decide. If it is too short, the supply gets concentrated in a small number of people and the coin gets accused of being a pump and dump. If it is too long and the price does not rise accordingly, no one wants to hold onto the coin because it devalues too fast. Normally if a (fiat) currency exceeds 4% inflation it starts to be a problem. I don't like Bitcoin's distribution curve (see http://www.mattwhitlock.com/Bitcoin%20Inflation%20logarithmic.pdf) because it takes a long time (12 years) to reach a good inflation rate (2%) and then only spends 4 years at that rate. I would prefer to have a initial period of very high inflation to distribute coins (like the first 4 years of Bitcoin) but then have a longer period where the inflation is kept at a constant rate between 2% and 4%.