For the first 15 years of my sales career I stayed at Holiday Inns all the time. They were everywhere and their Priority Club program was pretty good.
A lot of the older Holiday Inns are pretty run down. Many were sold off to Ramada and others when the franchisees wouldn't put any money in to them. The staff was always friendly, but the worn carpets, etc. just got to me.
I've stayed at a few HI Expresses and hated them. More similar to Marriott's Fairfield Inn than Hampton. As mentioned before, very sterile, cookie cutter like places. Service levels are pretty poor too.

I switched to Hiltons years ago, mostly stay at Hamptons as they are also everywhere now, not much more than Holiday Inns. When opportunity presents, I do prefer Hilton Garden Inns or Homewood Suites. I don't like overpaying at the Doubletrees, Embassey Suites, or the big Hilton properties unless I have to.

Not sure how the Priority Club ranks nowadays, but if it hasn't changed much, I would rate it over Hilton Honors.