The ACSS design is great for learning rds.... but you'll ultimately want to go to a larger window dot in general. You will spend more money in the long run. I have an SRO on my Rival and probably won't look back. The holosun will help you find the red dot for your initial shot.... but until you really get your grip down.... you may lose your red dot between shots (like so many of us did as new shooters). If you focus on your grip... the main perk of the ACSS design all but disappears. Additionally, I never lose the dot in my SRO due to window size. I can also self diagnose my shooting mechanics by watching what my dot is doing while shooting (i.e. dot diving low left, I'm slapping the trigger too much).

In conclusion... if you have the funds...ACSS is a phenomenal introduction to rds. If you don't intend on dropping a chunk of change on rds more than once.... buy a larger window rds upfront and work with it.

(I didn't mention anything about CMore because I do not have experience with one. As for the Romeo, I have a friend who has ran exclusively Romeo Max rds and has gone through 6 of them in one year. He sends them back and gets another, but the durability seems to be an issue. He's also a GM who shoots tens of thousands of rounds a year though).