Pros on liquid: easily dissolvable, easily measured
Pros on powder: shelf life very long. cannot be spoiled in heated temps, can be easily measured as well. might save you money.
Cons on liquid: can get spoiled from heat temps (im guessing) although i have no proof, i think it's very possible. some nutes say keep in dark cool place.
Cons on powder: cant think of any really. you gotta make sure it's dissolved and mixed well?
I would say go with powder. prolly have a lot better luck. i personally use liquid. maybe i should think about dry powder as well. measure, boom throw it in. i usually dilute my powders and mix completely before i toss it in my mix, i even have a bottle that i use to throw powders into to shake up to make sure it's completely dissolved before throwing it in. like a cocktail mixer. but that's just me. so maybe more work on the powder part. nothing like love for your girls tho!