This question has been asked before and tends to be met with the good old expression, "it depends". Depends on money you're looking to spend. Depends on work you're willing to put in. Depends on space you have. Depends on plants you're looking to grow. Depends on whether you want a constant, steady supply or are okay with big harvests every 3 months.
You mentioned "economical" in your original post. E&F and DWC are great methods for yield and speed. But with the water pumps and bubblers running as frequently as they do along with the lighting can jack up the electric bill and always run the risk of fire. Look up 'Hempy Buckets" and you may find an interesting option. It's a hydro-soil hybrid type of grow. No soil is used. Just perlite and vermiculite. No air stones or air pumps running at all. Just a bucket, a small hole 2" above the bottom of the bucket, and every other day watering. Solid results, similar yield, same finishing time, minimal fringe-electricity used, and fairly low maintenance (no rez changes needed...just watering). Haven't grown this way myself yet but I know a decent amount about it as I have been asking the same exact ? that you originally posted above.
If you decide to go ebb n flow, just go to Al B. Fucts thread (get a harvest every 2 weeks). He knows his stuff, gives detailed instructions and concepts, and his SOG method will never leave your father low on much-needed supply. Al B. is not on this very often so I would direct questions to a very skilled protege of his...Gypsy Bush. He won't give himself credit for knowing much, but trust me, the guy knows the ebb n flow method in and out and is more than happy to take on new learners.
If going DWC, I would recommend joining the DWC GrowClub and seeking out OnTheDL. Again, very skilled and knowledgeable about this method and very willing to answer questions. Roseman's threads are also a great source of info on this method as well.
With 3 400w hps, a 4x8 grow tent, and a medical user in need of regular supply, I would strongly recommend doing some variation of Sea of Green or Perpetual Harvest...at least in the beginning to get the regular supply up and running. It's a bit of work, but you'll never run out and never be dependant on the survival of just a few plants.
Also check out MBlaze's grow. He grows these trees that literally yield over a pound! You'll see Gypsy Bush attempting a similar method of growing. Less plants = less legal risk. Kinda changes the whole risk-reward ratio.
I apologize for not attaching links to threads to the grows that I am mentioning. In a bit of a rush. Just go to Search and click on Show Posts and then enter the names that I have mentioned.
As for pros and cons. Pros of SOG grows (some mentioned above) come in the easier manicuring process (this will drive you crazy). DWC is hardcore yield but takes a bit more time on maintenance and you will need to buy more DI or RO water. E&F is easier maintenance but still more than Hempy Buckets. Both DWC and EnF will use more electricity and be more maintenance than hempy. Hempy buckets I believe may have slightly less yield but not by much. I would imagine that it's more maintenance doing SOG with Hempy than it is with DWC or E n F.
Best of luck to you in your adventure and props for helping out your father with the medical care.
