The latter. Using Snapseed, I try to get the best colour photo possible, then convert to mono. Applying a Vintage preset and a Grainy Film preset, both with adjustments, gets me the toning and film look that I like. I just wish the Black & White conversion allowed me to play with the amounts of individual colours, in the way On1 Photo Raw does, rather than just apply a "coloured filter" to the result.
For any interested Snapseed users, the Vintage presets I use are numbers 6 and 7 with a low blend amount and with the vignette at 0 (I prefer the main Vignette so that I can place the centre); the Grainy Film preset I use is X03 with the strength set to about 50; and for the Black and White conversion, the preset I use is the Film one. At least, these are the settings I'm using for my current crop of mono shots. This will change at some point.