There was a time not to long ago when a vacuum cleaner was basically the same machine no matter where or how it was purchased. In previous times, the decision on what vacuum cleaner to purchase was based more on the "extras" the salesman offered but more often than not, it was the financing arrangements that were available.
Like now, most families could ill afford the additional expense of replacing home appliances, which few that were available. The vacuum cleaner though was one piece of equipment that was considered almost a necessity once it was used, especially with the advent of wall to wall carpet.
Many homes pre-1960 did not have wall to wall carpet but instead relied on area rugs for floor coverings. These large rugs could be taken out to the backyard, hung over a fence or clothesline and beaten with a carpet beater to remove ground in soil.
Vacuum cleaners removed the need to take rugs out of the house for cleaning. Today however, there are several carpet cleaning technologies available. Two of the most popular types of vacuum cleaner technologies include HEPA filtration and bagless.
Both technologies have the champions and like everything else have their positives and negatives. The positive with HEPA filtration is that small particulate dirt is better captured. This allows for a cleaner exhaust and theoretically, a cleaner indoor environment. The negative with HEPA type filters is that because they capture the finer dirt particles, they tend to need more frequent bag or filter replacement. Another potential issue is that as the HEPA filter captures more dirt, it also tends to lose some suction power as the filters fill.
Bagless vacuum cleaners are exactly what the name suggests. Bagless vacuum equipment typically features a cup or hard plastic container that captures the dirt during use. This makes emptying a lot easier and the amount of consumables like vacuum bags and filters is a lot less.
Consider not only the technology but the ease of use, general quality of the equipment, weight if you're going to carry it up and down stairs, etc. Onboard tools are nice but why carry around all that extra weight when not needed. Every vacuum technology has their share of people who love and people who hate it. The key is to find the vacuum cleaner you like.