So I am in SoCal and our temps are mild for the most part....it if get to 50 degrees outside it is cold here! lol Today the temps will get up to about 75. But in summer we get hit with a few months of 85-90 degrees. Ambient temps are pretty much going to dictate the temps in the box as you know. Right now It is about 72 in the room where my closet is. My grow area under my LED is around 75 plus or minus. My previous setup with my HID it would have ran about 78. Now that may not seem like a big difference but keep in mind with my 400 those temps are with my inline fan running 3/4 to full speed. With the LED I am 1/4 to 1/2 speed with my inline fan. For me that helped a lot as I like a more stealthy and quite setup. I adjust my setup and fan lower at night when temps drop and my closet will get down to about 72...that is still with lights on. I am veg at 20/4 now. So back when I bought my 400 I want to say I paid a couple hundred dollars for light with hood, glass, etc. The light bulbs run 60/80 and depending on how many runs you do may need to be replaced every year. The electricity is more than double with the HD going. So yes the upfront costs are more, I basically paid 500 out the door for my light. I prob save $20 month on electricity. I won't have to spend the money any replacement bulbs for a vary long time. So if you find the cost is double of what your looking at with a HID think about long term cost and you will make it all up year 1. I know not everyone has the cash in pocket but it is funny to see such a controversy about the light costs when your talking $250 vs $500. Now for the yield....well you sound like your like me and just want a modest setup for a couple plants and not looking to break any records for the largest colas in the world. I have yet to flower under this light but will be comparing it to my last grow. I had my HID pretty dialed in and got 7 oz from two plants last run. I am hoping for not much of a drop off with my AREA 51? Another thing to consider is the grower, a newbie might have a couple runs and then not be into it....maybe not have success or for whatever reason stop growing. Happens ALL the time....if that is case maybe it makes more sense not to invest more money upfront until you know this is something you enjoy and will keep at. If you do decide to go HID look into the CMH, they run a little cooler and have a better spectrum but I would try and keep to 400w and not go lower.
Also something to consider with LED is a lot of the lights actually need to sit a little higher above the canopy than I hid! Depends on lens angles but def look into that with your limited height. My light recommends 20" veg / 18" flower plus or minus.
