Less visible, wefts or strands?

Definitely.  The wefts lay flatter to my head, and although I love my strand by strand installs nothing beats how close to the top of my head I can put a weft in.  I'm not sure about installing with the silicone microrings, since I imagine it would have the same visibility as strand by strand microrings.  I installed my sisters hair with shrinkies and wefts....but for the top I used strand by strand shrinkies.  The weft methods I have tried so far have all been bonded with some kind of sticky stuff.

My favorite install so far was with the silicone microrings (so far I have latex glue, liquid gold, protac, extentubes, shrinkies, and silicone microrings under my belt) but I did put them up high and if I didn't do some strategic styling a few would always manage to fine their way out lol.  I have yet to fine my weft showing, although now I am using the handtied there was extra string that I didn't take care of and did notice a nice blonde peice of thread hanging out of the side of my head the other day lol.

Good luck!!

I cant tell you how many people said my sewn in weave looks 100 times better than the fusion. The coverager is better in the back and blends better with my hair and you dont see little glue bonds if the wind blows. I can also now wear my hair in more hairstyles than with the fusion

i have also found that wefts are less visible but i like the moveability of the strand by strand.

I agree with everyone that wefts are less visible.  However, I don't like the 'stiff' look it gives my hair due to the lack of individual movement, and I also find that it makes my hair on the sides too flat looking.