I have 2 guitars to replace tuners on, 1 mex '90s strat , and an old ES 335...I don't care about the ease of changing strings (i.e.locking tuners), just want to know which tuners keeps the string held in tune the best . I'm considering Grover non-locking, and Sperzel locking tuners-any opinions on which works best regarding tuning, been getting conflicting opinions with my collegues.