Eve smite color?

I've seen master/challenger jungles go both purple and red smite on Eve. For the most part it seems to be preference between easier clears for more HP and gank pressure, or damage w/ E which boosts autos and has synergy with red smite (thus bringing more damage to the gank for pressure). I'm wondering if I'm on the right line of reasoning and what situations would influence the choice to go either way? I played a lot of jungle a season or two ago, but have played very little this season and am hoping to get back into it as a main role bc I like it, so I figure purple smite may be a little more valuable until I get my gank timing down a little better (gank more often bc I'll likely fail more often, rather than bring more dmg and gank less often).