Which of these is better and why?

    button .b
    rename .b .b:cmd
    proc .b { args } "eval [list WidgetHandler .b] \$args"

or

    button .b
    rename .b .b:cmd
    interp alias {} .b {} WidgetHandler .b

[MS] prefers the second, for both clarity and performance reasons (no string parsing at run time).

[PWQ] An alternate for the first would be:
	proc .b {args} {uplevel 1 WidgetHandler .b $args}
So that the widget handler has access to the callers namespace et al.

[Vince] does anyone have performance data on the different approaches?  Note that the proc should be:
	proc .b {args} {uplevel 1 [list WidgetHandler .b] $args}
for optimal performance, I think (but haven't tested!).

[RS] Widget handlers in UIs probably don't make a difference if they run a few milliseconds longer. I'd go for the version that is easiest to read. Oh, and the [list] grouping for uplevel is not necessary, as both list elements obviously have no whitespace in them...