Depends on the bike and accessories. Years ago when I rode a typical cromoly frame 10 speed with drop bars, fairly quick Continental tires and toe clips, I found it easier to climb some hills by climbing out of the saddle. I wasn't a strong climber and it was easier on the knees. But on long distance rides stronger riders would pass me while they were seated. So it wasn't fast, it just felt more comfortable for me, with less thighs-on-fire.

But with my current bike - a comfy/hybrid type, with upright bars and platform pedals - standing to climb feels less secure. The high handlebars and overall geometry aren't quite right for this technique. The platform pedals without toe clips demand more attention to foot placement. Mostly it offers a bit of a respite for the knees and thighs when I'm tired.

However a couple of days ago I adjusted the saddle forward very slightly and over the last couple of rides I'm finding it more comfortable to remain seated on uphills and lean my forearms across the high handlebars and shift the balance and weight just enough to use the thighs more efficiently.

Also, I've stopped pedaling exclusively on the balls of my feet. I was locked into that technique with toe clip pedals and Detto Pietros years ago. And I continued to emulate that position when I resumed riding several weeks ago. But there's really no valid reason for it, and I'm finding it more efficient with platform pedals to shift my feet forward slightly and center my arches over the pedal for climbs or into headwinds.

That's one reason why I might add casual pedal straps, but won't get clipless pedals/shoes or return to toe clips. For casual riding on errands and pleasure rides up to 20 miles, I prefer being able to shift my feet around to get comfortable as conditions change. And, while I was comfortable with toe clips 30 years ago in traffic, platform pedals are more comfortable in traffic for me now.