A RDS isn't going to be a panacea when you first start using it. It will take a bit of practice to get comfortable with it. I initially didn't like a red dot as it took too long to find and cost more money to configure the weapon (both optic and optic cut).

My initial foray into a RDS was with a T1, which required no smithing to my Glock and I already had the optic. I found the tube to be easier to use and find the dot than a prism system. As I continued to practice with it, I really grew to appreciate the RDS concept. I found I became more accurate with follow up shots (to a point), and not having to find the front sight was much easier on the eyes. Once I became a RDS cripple, I found some reasons to go back to a RMR-type setup and have been spending my shooting time with that the last 6 months or so. One way to learn how to find the dot quicker with a RMR-style is to not look for the dot, but start to find and align the sights. They don't have to be perfect, but as they come into view, so will the dot and you can transition to it.

I find not only am I more accurate with a dot (be it a 2 MOA or a 3.25 MOA dot), but it also has made me a better shooter in seeing the errors I'm imparting into the gun when shooting. I don't mean the dot twitching around when it's on target. Instead I mean seeing where the dot goes at the trigger press. It helps diagnose errors you're putting into the gun and also helps with "calling shots" an knowing if it went where you think it did...no different with a rifle, but more sensitive. I spent a lot of time on a B8 at 25y using a dot to narrow down why I couldn't break 90 consistently. It was a big help, and a laser training gun wouldn't have shown what I was screwing up.

As for which one, the Holosun seems to have great reviews. I haven't personally looked through one, but have used an old Docter and regularly use a RMR. The RMR has the one issue of needing to be rezeroed after every battery change, but it's not like you're starting from scratch and it doesn't take that many rounds to rezero it. The Holosun doesn't have that issue.

One thing I have found with a lot of mini-RDSes is the coating can cause ghosting of the dot when the sun hits the lens from certain angles. I've seen it happen with a Delta Point, where 5 dots appeared on the lens because of how the prism was catching the sun light. The Docter did this as well. The RMR coating eliminates most of this ghosting, so you might get a slight secondary dot, but the primary dot is clearly the one to use when that happens. I haven't been able to see if that happens with the 507. This may not be an issue for you, but at the range I shoot at, one of the primary firing directions is into the sun in the first half of the day, so depending on the time of year, it happens regularly. Another reason I'm happy with the RMR, since this isn't really an issue.

Sounds like the 507 may be the answer for you for now. Lower cost to entry and it has a RMR foot-print, which everyone knows how to cut in slides.