sun ligth vs. 400w hps

So I've been growing indoors under a 400w hps and im wondering if for veg or flowering is it any good to alternate from sun light to lamps when the sun goes down? or is it bad for the plants? I've been doing to my seedlings and they seem to love the sunlight and even tilt towards it. scared to do it to my flowering plants tho. Anybody else done it? should have better result right? The sun does provide better lighting so i should get some denser fatter buds?

i done it on a flowering clone. just for shits &giggles,but she done good,tried it on my current veg plants .was growing slower than im use to. so i pulled my 400mh lamp and you can watch them grow,which makes no sense .sun suppose to best ,all i figured its was late,but im vegging mh all the way .plus you take chance on bring unwanted pest in your grow space..( selfexperience taught me this)

i was thinking along the lines about leaving them on the windowsill for half the day then put them back under lights for the last hour untill they turn off

I have brought my plants outside and brought them back in throughout their whole life cycle, they love it, the sun is the strongest light you will ever find, its equivalent to a 1200 watt light, I dont know if thats true, but I saw it in a video of someone who seemed to know what they were talking about