I have not seen any studies directly comparing the feminization effects of the different methods of administration.
My personal preference is for sublingual twice a day. It works for me. Other people may have a different experience. My opinion is that when someone complains that their method is not working is really a complaint that it is not working fast enough for them to reach their goals in terms of physical changes. Hormone therapy takes time, often two years or more.
Until more research is available, the best advice I can give is get your blood levels into the normal female range and keep it there for several years. Keep in mind that blood levels can vary throughout the day with sublingual administration. To see the lowest level (trough) have the blood drawn before you take your daily dose and to see the highest level (peak) the blood sample should be taken within one hour after you take your daily dose. Injectable and patches being much longer half-lives, do not have this problem as dramatic as sublingual administration.
To summarize, steady state blood levels are not that important for feminization. Even cis women have hormone blood levels that vary throughout their monthly cycle. It seems to work for them.