This is a common argument against twins and its lack of validity is easily established. The chances of an engine failure don't matter. What matters is the options you have available after a failure.
I always like to present the following scenario to twin nay-sayers. You and your spouse are on an island. Your spouse develops a strange illness and needs medical attention on the mainland ASAP or impending death could result. No ferries available, no boats to rent charter borrow or steal, no scheduled flights or charters planes available.
The airport operator has two planes he'll let you borrow. A single and a twin. But he warns you that both have wonky engines and it wouldn't shock him if either one had an engine failure in the next 40 minutes of flight. The mainland is a 90 minute flight. Assuming you're current and proficient in both singles and twins, which one you gonna take? I defy anyone to pick the single in that scenario.
Next time I'm in that scenario I'll let you know what I end up deciding.
(Sorry, couldn't resist)
Tim