The main issue I've encountered with 700c is finding the right compromise between frame and tire size.
For my errand bike I want heavy duty, puncture resistant tires. That effectively makes the frame higher. So I'd need a smaller frame, if it's a bike with a horizontal top tube, or a compact frame bike with sloping top tube.
My main errand bike's compact frame is technically slightly small for me, but with the 700x40 Michelin Protek Cross Max (which actually run closer to 700x45), the effective riding height is just about right.
I occasionally use my older hybrid for errands. With the horizontal top tube and 700x42 tires, the effective frame height is slightly tall for me. It was originally designed for 700x32 or x35 tires. So it's a chore to hoist a leg over the bike with the taller tires, when the bike is loaded with groceries.
If I had to rely on my horizontal top tube hybrid as my main errand bike I'd probably switch to 700x32 or x35 Michelin Protek or Schwalbe Marathon tires. You wouldn't think that 1/4" to 1/2" height matters, but it does when the rear rack is loaded down, especially when stuff is stacked above saddle height.
If I intended to buy a bike specifically for errands and hauling up to 50 lbs loaded directly on the bike in baskets or panniers, I'd go for a compact frame with sloping top tube and 26" wheels. That way I could step across the top tube when the rear rack is loaded higher than saddle height.
And there's a good selection of affordable heavy duty 26" tires, ranging from the Maxxis Hookworms to the Michelin Proteks I like.