Gmail has this capability built in because you can just add +whatever to the end of the name and it's an alias to your email account, and you can block the yourname+whatever@gmail.com it as needed. Only problem is many sites mistakenly think + is an invalid char.
No overhead of creating addresses, you have an infinite address space for your account to play with freely.
You're still correct though, your solution is more secure (and also what I use). It's always possible the form you submit automatically strips the +whatever from your email silently. I believe facebook does this (at least when checking to see if the email you're using has already been registered).
The one downside I've found for this is that many email forms prohibit "+" in an address. They shouldn't as it's a perfectly valid character for an email address, but you know...devs.
I used to use the + system but ran into too many issues of it not being accepted and it seems some are smart enough to strip off the + and everything after.
I moved to wildcard forwarder on my own domain so that *@mydomain.com get forwarded to my main email account. This gives me all the tracking I want and I can ban addresses if needed.
That still gets me the zero overhead and practically infinite addresses with none of the downsides of gmail--and I can easily change my main email account as an added bonus.
No overhead of creating addresses, you have an infinite address space for your account to play with freely.
More mail providers should offer such a workflow.