I know this isnt what you asked but neither. I recently had to buy a new washer and spent hours researching whether to buy a top loader or front loader, impeller or agitator, etc. please check out the yale appliance blog for information on why front loaders are the best at energy efficiency and cleaning your clothes the best. if you must get a top loader get an agitator. Impellers do nothing (again check out the yale appliance blog).

In terms of the question posed, an impeller is unacceptable. I just spent the last week using my Mom's Maytag with an impeller (we have family here in TX who have Samsung or LG TL HEs and it is the same thing). When the tub is filled with enough water to somewhat submerge a large load, there is no turnover at all. Merely a movement at the top of the water line. When the cycle selected is one where it is going to sense the load, everything is at the bottom fighting for what water there is. My recommendation is an agitator if one if choosing between the two types of agitation devices.

Many toploaders nowadays with a centerpost agitator really are impeller-type machines ... the base of the agitator is an impeller design. (An impeller technically is an agitator ... any device in the drum that swirls/moves the water and clothes is an agitator.)

There's a lower-end Amana (manufactured by Whirlpool) model with a true dual-action agitator that regular fins on the base and a spiral upper section that rotates one direction to push the clothes down. Majority, if not all, of the other brands and models have a fake auger that doesn't turn separately in one direction. It rotates back-and-forth with the base and jiggles the clothes both up and down to no effect of promoting rollover.

Speed Queen model TC5 has a regular agitator but it doesn't have a spiral auger. It's a popular choice among people looking for an "old-style" toploader ... but be aware that it has no control for multiple fill levels. All the cycles fill to one standard level (Normal Eco = 13 gals; Heavy Duty, Perm Press, Delicate = 14.5 gals; Bulky/Sheets = 16 gals) or a slightly higher level with Deep Fill option selected (16 gals Normal Eco, 19 gals all the others). Can't get less than 13 gals for a small load or single item.

Check out the videos on Youtube to see how useless the washers WITHOUT the agitators are.

Older impeller models had stronger wash action. Latest designs nowadays are lethargic, either because the speeds are reduced or the impellers are lower-profile than earlier versions.

This is a 13yo model that works nicely. Fourteen shirts in this load on HE (low-fill) mode. The beginning shower is a pretreatment function. The wash period begins at 7:10. Takes a couple mins to get the load mixed-up and moving.

I'd rather buy a washboard and sit on the bank of the muddy Mississippi and wash my clothes, lol.

Yay! Show us your riverside technique!

dadoes, haha! I am really too old to do that. I could go swimming in a chlorinated pool with them!

In CR's testing the best HE (i.e., non-agitator) washer outperformed the best agitator washer. However, there were many poor-performing HE washers so just buying an HE washer does not in any sense guarantee good performance. You must select an appliance not the type of appliance.