Recommended method for reloading `.zshrc`? (`source` VS `exec`?)

Most people seem to recommend using source for reloading .zshrc. Why?

First I tried out source ~/.zshrc. But it resulted in a compinit error (at reload, not for new shell instances at first .zshrc load).

My reload alias is now:

alias zsh-reload="exec zsh"

instead of:

source ~/.zshrc

The reason for this is that my previous reload method (source) triggered a compinit error;

zsh compinit: insecure directories, run compaudit for list.
Ignore insecure directories and continue [y] or abort compinit [n]?

So I'm now doing exec because I believie it ensures the previous environment doesn't pollute the new one.

• What are the downsides of using the exec method?
• Is there an explicit reason for that you're doing exec or source?
• Could exec in theory cause unexpected problems compared to the source method?

With exec, all (unexported) variables in your shell are lost, which is probably not what you want. Instead, it might be better to fix the compinit problem, by using compinit -i. See the zsh man page for compinit, paragraph Use of compinit:

to make compinit silently ignore all insecure files and directories use the option -i