A pity you can't reconsider your vote and vote again, then, Geordie.
How much research do you think you'd need to do on the Henrys before having enough knowledge to make a definite reconsideration?
Well, for study and pleasure, I've read fairly extensively about the Wars of the Roses, and therefore about the last Lancastrian, Edward and Richard. My knowledge on Henry's IV and V is more on the level of having attended lectures and light reading concerning the two.
The others, I've read well regarded scholarly books and articles on, so like to think I can make a decent judgment. I have a soft spot for the Yorkists, but neither of them were 'good kings', all things considered. It would take more than a Wikipedia article or two to convince me that Henry IV was more effective than his son. The victory of the latter is more down to the competition than his own prowess. If Agincourt offends your sensibilities, then I'm not sure how a usurper who lied his way to the throne is much better though. The Wars of the Roses also saw plenty of summary executions...
For the record, I haven't actually voted.