I have found that it depends how you pay for the upgrade. If you use USD then there is no difference in my opinion. When I used a cryptocurrency to upgrade, I have found that buying a larger amount is beneficial. It mostly has to do with the number of decimal places allowed for the cryptocurreny transaction. For example, when buying an upgrade with BTC the BTC price is down to three decimals. Obviously, as the BTC price increases there is quite a difference between decimal figures.
Have a great weekend!
Steem on,
Mike