Of course sticking to IOF as an all year round tariff.
But best all round tariff, no, it’s not, especially if you are a low energy user.
Assuming you don’t have an EV or a heat pump so your choice of tariff is limited, check the rates on IOF, Flux and say Economy 7.
What is unique about IOF is that you get the same rate for export as you do for import so if you have a larger solar array than your house consumes then in summer you will built up a good credit on your account as you will be paid an export rate of 23p (or whatever your regional variation is). This is far and away the best export rate and any import you make overnight will be at the same rate.
But in winter when you are generating very little so everything is import then you are importing at 23p which is not a particularly good import rate.
Taking Economy 7 as an example, the overnight rate is 14p so if your batteries are sufficient to meet your house demand for a whole day you could charge overnight and all your electricity would be at 14p (less conversion losses) - a saving of 9p over IOF.
Of course you might not care about the saving, IOF is simple and you don’t need to program any charging of your battery, Octopus do that for you.
A lot of people will have one tariff for the summer (often IOF) and another for the winter. Changing tariff with Octopus is simple, it usually happens within an hour of the request. But personal choice as ever.