I dont believe I would be concerned with simplified programming point of view. Honestly, it is not like you change light patterns every day. Once you figure it out and define what you want - you will not be chaning too much.
I personally like the idea of being able to controll different light temperature via two seperate units - lets say you may have island with SPS that need more 16k look, while on the other part of the tank you may wish to go with acans, chalices and you want 21k to display their vibrant colors.
but for the bigger tanks 180g + you simply have bigger area to cover. so lets say right now you have 90g tank and you take two IO units. what do you do if you upgrade to 210g?
I just want to avoid a situation when someone buys rather expensive light and doesnt look into the future and may not be happy once he upgrades. these are not cheap lights and I would rather make sure that everyone goes over every single detail before making a decision. I have no problem answering any and all questions on here, via email, via phone or via PM.
I posted PAR readings on 160W so PAR penetration with IO will be identical with the exception of the coverage area. smaller unit, smaller coverage area. so IO will still reach above 200 PAR at 29" just like 160W, but the coverage area will be smaller. so I do not worry about PAR per say on bigger tanks, unless you are talking on 36" plus. even 30" - if you think about it, there is a sand, corals are on the live rock, you gain back about 10".
Are you recommending this solely on a simplified programming point of view?
Are you implying that larger 120+ gallon tanks also tend to be deeper and therefore require the 90w\160w light at a minimum?