I have a manual mini-Presidio and a Para. I don't like autos or A/Os so I don't have any of them, although I've handled a couple in the past. The Para is the only one of the two that I use and I use it for everything hard and dirty... same things I use my SnG for.
Understand that my 525 has not failed in any way. I did carry and use it lightly. Everything worked fine on it. It just ain't my cuppa tea.
I prefer the Para for the ergos of the handle, the open construction (harder to collect junk and easier to clean out), and the ruggedness and simplicity of the compression lock.
If you're concerned about quick, one-handed openings, the Para should be a fine fit. The Spyderhole is large (and ambidextrous

) and the compression lock is also easy to operate with either hand for closing. Plus, it's a very simple, manual system, and I see a lot of strength in simplicity.
I also prefer G10 to aluminium for scales. Both are tough, but the G10 is going to be less subject to temp variations that might affect your grip and if you drop a G10 knife, you're not going to be able to tell it from the handle scales. Aluminium does ding and scratch.
154CM is one of my 3 fav SS, but so is S30V and I've had zero problems with any of my S30V knives. It'll hold an edge for you a little longer than 154CM, although it'll also take a little more time to sharpen it up if it gets dull. Keeping it sharp doesn't really take any more time than any good SS if you do it in a timely and consistent manner.
The only... I say the ONLY... caution I would issue about the Para is to be "somewhat careful" of the tip on the blade. If you don't pry or remove screws with it, you should be fine. I've never broken a tip on any of my Spydercos and I don't baby them. But sharp, fine tips are a feature of this type of Spyderco blade. It's a function of the blade shape, not materials or QC. Those are all top-notch with Spyderco as they are with Benchmade.