I'm a little unclear on the question -- sounds like you think life in prison is better than death (for the convicted person, anyway), given your list of good things that life in prison allows (but death doesn't). So you already do think the death penalty is worse for the convict than life in prison?
Or are you (implicitly) arguing against the death penalty, by arguing that it's not worse than life imprisonment, and therefore there is no reason to apply it to the worst criminals?
In any case, one consideration that it's worse for the convict to receive death is simply that very many convicted persons simply don't want the death penalty; lots of people are terrified of being killed, and that terror alone makes the prospect of death seem far worse than life imprisonment. (Of course you might argue that this is an irrational fear, but that then takes you off into all sorts of other issues and directions ....)
And if the ultimate concern is whether our society should allow the death penalty, it's worth mentioning that there are many other things in play in addition to 'how bad is death v. life in prison for the convict' -- including issues of justice, of fairness, of the rights of the victims (and victims' families), etc....
Hope that's useful--