I should back up and address the op's question.
I have a summit press
I also have a co-Ax, a pacific 0-7(old hornady single stage),a lee classic And a lee hand press.
My ideal press aside from a co-ax would be a Redding A-7 turret (some future purchase - see johnny's reloading vids on YouTube).
the summit fills a niche for me in that it is great for portability since you don't need a bench to mount it while still being heavy enough to do decent case sizing. I take it to my hunting "glamp" mounted on a piece of 2x10.
There are 2 versions of the summit, the old one with 2 screws (inexpensive on eBay in redwhitandblue -mine) and the current model with 3 screws which addresses some of the reliability issues with the old one.
On the summit, the die moves down on the case instead of the case moving up into the die.
No real difference in performance between the summit and the hornady "o" type press except the inherent strength and on-press priming. The summit doesn't have an on-press priming option so you will need a separate priming tool- either a hand primer like the rcbs and lee or bench mounted like their other versions or a lee priming die like the one included with their hand press.
For 223 loading the summit will perform well and will be as reliable and as precise as most.
If you are not doing difficult resizing tasks (sounds like your not) then the summit will work well. I bought the short handle for the summit to make it more useable on table tops and lube cases well without any problems in sizing to date. Proper lube is key.
you won't have as much leverage as with the co-ax or some others but you shouldn't need it. The on-press priming of the co-ax is way over powered and I have ruined cases by trying to "feel" the primer seating.
Best wishes and I guarantee that whatever press you buy, it won't be your last.
Ps your rcbs junior is a competent press that a lot of competitive shooters use...