I use the first style you gave:

Options[tListPlot]=Join[
    Options[ListPlot],
    Options[tLegend],
    {
        Rule[ShowLegend,False]
    }
];

The function is then defined as

tListPlot[data_,options:OptionsPattern[]]:=...

I don't see any reason to use SetDelayed (:=) in this context. EDIT As Brett Champion mentions in the comments, the default options for

System`Plot

will change if you use SetOptions on Plot. Hence, if you want your custom plot to always have the same options as Plot, use :=. I would prefer to specifically change the options for my Plot separately, so I would still use simply Set (=).

You might also want to check out this instructive question on Options in custom functions: Functions with Options

I use the first style you gave:

Options[tListPlot]=Join[
    Options[ListPlot],
    Options[tLegend],
    {
        Rule[ShowLegend,False]
    }
];

The function is then defined as

tListPlot[data_,options:OptionsPattern[]]:=...

I don't see any reason to use SetDelayed (:=) in this context. EDIT As Brett Champion mentions in the comments, the default options for

System`Plot

will change if you use SetOptions on Plot. Hence, if you want your custom plot to always have the same options as Plot, use :=. I would prefer to specifically change the options for my Plot separately, so I would still use simply Set (=).

You might also want to check out this instructive question on Options in custom functions: Functions with Options

I use the first style you gave:

Options[tListPlot]=Join[
    Options[ListPlot],
    Options[tLegend],
    {
        Rule[ShowLegend,False]
    }
];

The function is then defined as

tListPlot[data_,options:OptionsPattern[]]:=...

I don't see any reason to use SetDelayed (:=) in this context. The default options for

System`Plot

won't change at any point (until you install a new version of MMA), so you can safely just use Set.

You might also want to check out this instructive question on Options in custom functions: Functions with Options

I use the first style you gave:

Options[tListPlot]=Join[
    Options[ListPlot],
    Options[tLegend],
    {
        Rule[ShowLegend,False]
    }
];

The function is then defined as

tListPlot[data_,options:OptionsPattern[]]:=...

I don't see any reason to use SetDelayed (:=) in this context. EDIT As Brett Champion mentions in the comments, the default options for

System`Plot

will change if you use SetOptions on Plot. Hence, if you want your custom plot to always have the same options as Plot, use :=. I would prefer to specifically change the options for my Plot separately, so I would still use simply Set (=).

You might also want to check out this instructive question on Options in custom functions: Functions with Options