This is a huge question that has many people seeking me out for an opinion.
This is not a simple matter. As always, there are factors one must take into consideration. The first consideration I would think about is time. Sativas take a fair bit longer than indicas to mature and be harvest-ready, around 4-12 weeks longer depending upon genetics and grower preference for harvest. Sativas tend to require a fair bit of room as a result of this, and this tends to put off many potential growers. This tends to relegate sativa cultivation to larger grow rooms or outdoors. Ruderalis-based plants will be easy to grow indoors or outdoors, and will pretty much to their own thing as long as you give them water and nutrients and light, you don’t even need to time the light in most cases.
The next consideration is space. Indoor growers may not have adequate space to work in, and as such short and squat indicas, or even ruderalis hybrids are recommended for maximum yield per given volume of space. Indicas also tend to respond very well to training and produce much higher yields versus sativas. Ruderalis tends to yield a bit lower than sativas or indicas due to their auto-flowering trait which makes it near impossible to get plants as large as one might like for desired yield. When you choose a strain, do a little research. Check for your yield per square meter (or square foot if you prefer and they list it.) This will give you an idea of how much space you might need, and how much you might expect to yield under optimal conditions for a given space.
Potency is another thing to keep in mind. The common belief is that sativas are for the head, indicas for the body. I’ve personally had plenty of sativas that would give me incredible body-numbing effects, and plenty of indicas that gave me soaring head effects, so I would take that bit of wisdom with a grain of salt. This is really all dependent upon how the plants have been bred over the years, and as a product of the breeding, the particular cannabinoid concentrations found in said plants. Many seed banks and cannabis books have information on particular strains with known cannabinoid contents, these are great resources and you should be able to find them at book stores, cannabis forums, and online from breeder sites and seed banks.
A final consideration, mostly for those in non-medical states, would be stealth. Obviously, due to their tendency for height, sativas are not very stealthy except when kept trained and trimmed under a regular regimen. Indicas are easier to keep short, however they can have extremely pungent plants during flowering, and the smell can go everywhere without proper air filtration. Ruderalis hybrids will be very dependent upon what their progenitors were regarding height and smell. Larger plants will require more energy, if that is a concern for you, but paying your bills on time should be the most effective deterrent to that worry, and by all means, DON’T STEAL POWER! Also, the larger the grow, the more likely you are to be busted due to maintenance and supply requirements. Traffic is traffic, and lots of traffic tends to get noticed.
If you want my personal opinion, I prefer a good hybrid of sativa and indica, such as Hindu Skunk. You get good yield, excellent quality, it’s easy to maintain and isn’t as picky as other strains with regards to nutrients and growing conditions. Grown under LED or LED/MH or LED/HPS or HPS/MH combo, you can get incredible results with potency far above what is typically listed, with flowers that look like Superman’s Fortress of Solitude under a microscope.