I use only powders, to avoid gunking up the outer drum; I have a front loader. Also, I don't have a laundry sink, so I prefer to avoid the gumming up of the measuring cup I used to get with liquids (if they are coating the cup, are they coating the outer drum as well?)
I generally use European powder (Henkel Persil, Unilever Persil/Via, or P&G Ariel) brought back from European visits (or I ask people visiting from Europe to bring a packet over for me) for my work clothing, which is office casual. For towels, linens, cottons (jeans, t shirts) I use Gain HE or Tide HE powder and conserve the European products for my work clothing. In the past I have bought Gain and Tide from Amazon at prices lower than the big box stores, by buying four-packs. Yes, you get a Costco-sized amount of detergent, but it works out to cost less than at a retail store, plus it's delivered to your house. I happen to have AMazon Prime, so I get free two-day shipping, but the Gain and Tide I have at home were purchased from Amazon before I signed up for Prime, and were shipped free because the order was over $25.
I have a Frigidaire 2140 (3.5 cu ft) and I use a coffee scoop (30 ml/2 tbsp) to dose detergent. On full loads, I use 3/4-1 scoop of Tide or Gain, and 1/2-3/4 scoop of European powder. So I am using roughly 2 tbsp of Tide/Gain or 1-1.5 tbsp of Euro powder, maybe a bit more for very large/heavily soiled loads. The result is that I go through my supplies so slowly that a large box of Gain or Tide lasts over a year, and my Euro supply lasts for years too. I brought back four boxes of Ariel from London in 2011, and still have three of the four boxes left. I"d never use what P&G recommends, or I'd be oversudsing the machine. By the way, Henkel lists the number of loads on its containers as well, and they seem to based on very high dosing which I'd never do, hence my package lasts way longer than the container would suggest. We have hard water here, I don't have a water softener, and I get excellent results using the amounts above.