Besides the usual differentiators for electronic gadgets (like brand, warranty and support characteristics in India for both domestic and international manufacturers) and specific ones for washing machines like size and features, there are two main types to choose from: front loading and top loading, depending on where the door is.
Secondly, the machine can be an horizontal axis (or h-axis) one or a vertical axis one, depending on how the washing drum in the machine is oriented.
Typically, front-loaders are h-axis machines and top-loaders are v-axis. However, in Europe, particularly in France, top-loading h-axis machines are popular. And my research tells me that they're the best of all worlds.
As distilled from Wikipedia and Google results, front loaders are universally better than top-loaders when it comes to the actual washing. They are ultra-efficient in using water, electricity and detergent. They're also much more gentle on clothes because they use gravity to shake clothes around rather than have a harsh motor-driven agitator that stretches clothes and reduces their lifetime. And they also supposedly result in much cleaner clothes than top-loaders. In addition, because they're capable of much higher rotation speeds than v-axis machines, clothes come out much drier than top-loaders. All these advantages come from the fact that they have h-axis drums.
Front loaders do come in second however, when it comes to ergonomics and price. Because the door is usually low, one needs to kneel or bend to put clothes in or take them out. For elderly people or people with bad backs, this is a deal-killer. They're also generally more expensive than top-loaders – top-loaders start around ₹6000 and front-loaders start around ₹15,000 (check out the latest pre-discount prices at compareindia.in.com/products/washing-machines/). Top-loaders are much better for loading and unloading and for your wallet, though they are a bad deal when it comes to all the other aspects. There are innovations like the Godrej Tilt Drum Washing Machine where the h-axis drum is slightly tilted upward to make it easier to load and unload. I haven't been able to see one of these in person however anywhere in Mumbai - I've hunted for them at Vijay Sales, Croma, Sony Mony and other places all over the City.
Imagine my delight when I found out that there are machines which combine the best of all worlds, the advantages of top-loading with the benefits of an h-axis drum. They're also called top-load h-axis washing machines. Made by Miele or AEG, they're ubiquitous in places like France. Unfortunately, they haven't made it to India. Not yet, anyway.
Researching the world of washing machines, and all the amazing advances made in this technology, seemingly mundane on the surface, has been fun and quite revelatory. While we take them pretty much for granted these days, it's been interesting to delve into the nitty-gritties of how they actually work, and the minutiae of their various features and USPs. As for me, I finally decided to go with a front-loader as I'm too much an environmentalist to reconcile myself with a top-loader v-axis machine. As for the bad back issue, we're going to put the machine up on a platform so that the door is at stomach-height, making it easy to load and unload clothes. A decidedly low-tech, straightforward and Indian solution to the problem :).