Does the difference between 90% and 99% modelling quality actually change results, or is it strategy tester vanity?
I assume the answer is "it depends", so the real question is: for which strategy types does it matter, and for which can you stop worrying?
It matters enormously for scalpers with targets under ~10 pips — the spread and tick path inside one M1 bar decides the trade, and generated ticks invent a path that never happened.
For H4 swing EAs with 100+ pip targets I reran identical tests on both qualities: results differed by under 3%. Match your data budget to your trade duration.
Also: real ticks versus generated ticks matter more than the % label, and variable spread matters more than both. Variable spread alone has killed most M1 scalpers I've seen that looked brilliant on fixed spread.
Clear — so for my M15 system targeting 25 pips, real ticks + variable spread is worth it, and I can stop obsessing over the percentage number. Thanks.