where abouts are you from ? There are some site sthat don't allow the use of HUDS ,which wouldn't put you at a disadvantage against other players that may be using them. SKY and Unibet are like that. HEM 2 and PT4 both give a 1 month free trial as well ( although PT4 has an annoying trial mode banner over each table when you use it during the trial. HEM and PT are now the same company so get the one that works best for you or that you like the best.
If you want to wait before buying , consider the hud free sites, or 888's snap poker is hud free whereas conventional tables can be used with a HUD.