Execution is less of a punishment to a criminal but, while leaving someone in prison for life without parole is a punishment it is also a burden to our tax dollars. If we execute a criminal we are ending their suffering they don"t really get punished remember we all die eventually. While on the other hand leaving someone in prison is a punishment to a certain extent, they get free meals tv provisions etc.. payed for with Americans tax dollars.
i hope this helps some sorry its a bit long