Matcha is not always lower quality than sencha. Matcha comprises some of the highest quality tea in Japan, but it also includes some of the most average. The matcha you get at a sushi restaurant in the U.S. is the latter variety.
I have made matcha at home. I bought a little canister of matcha powder from Nippan Daido grocery. It is high enough quality that they keep it refrigerated. I got a bamboo whisk off of ebay for a good price. Very nice whisks are made by hand by master craftsmen and can cost quite a lot of money. I think mine was less than $10, but it works very well.
I found some instructions online. I don’t remember where, but it’s very easy to make. Basically, you heat the water (about 180 F, you might heat it to 185 or 190 if you are pouring it into a room temperature bowl- so that the tea can bathe in 180–185 water…actually the ideal temperature depends on the tea and the desired result, so experiment freely and take notes), pour the water into the bowl, and get your whisk ready. Add the matcha (about 1 tsp). It will tend to clump, so whisk early. Whisking is back and forth and in a kind of Z pattern across the bowl. Whisking is never circular. You should whisk as quickly as possible and change the elevation of the whisk in the tea- sometimes whisking at the top lightly, and other times whisking in the middle a little more heavily. Whisking in this way takes practice, but it’s fun. You should whisk long enough to make a kind of froth from air being incorporated into the tea. Remove the whisk and rinse it immediately. Never soak the whisk or wash it in the dishwasher. It is delicate and the tines can bend or break. Rinse with cold water and air dry.
Now, the thing about matcha that is most difficult is waiting for the tea to cool. The Japanese say that if you can’t handle hot liquids you have a “cat’s tongue”. So apparently, they feel that you should be able to drink the tea when it is very hot. However, I prefer to let it cool for 3 to 5 minutes before trying to drink it. In this time, the froth subsides and the color of the resulting matcha can be seen more clearly. I use a black tea bowl.
The tea is very intense in flavor (if the matcha is good). You are also consuming the whole tea leaf so you are getting maximum benefit from the catechins and other health-promoting compounds. It’s also high in caffeine, and you may feel a buzz if you’re not used to it.
Matcha is expensive because of the way it is made. High quality, minimally processed, tea leaves are ground very slowly in a stone mills. The grinding must be slow to avoid heating the tea and destroying the delicate compounds. I read somewhere that it takes an hour to grind enough tea to make an ounce of matcha. This seems somewhat unlikely, but take it for what it’s worth.
As for sweetness, this is certainly possible. Tea plants which are fully shaded just before harvest have reduced tannins and have a naturally sweet flavor (the tannins are created by the plant to protect it from direct sunlight). Tea leaves made from this are called Gyokuro (Jewel Dew). It is the most highly prized type of tea leaf in Japan. Matcha made from this could have some sweetness also. Personally, I prefer sencha (which is grown in full sun or partial shade) because it has a more intense flavor and grassier notes, which I like.
Welcome to the world of Japanese tea! I’ve been drinking sencha almost daily for many years and it is one of my most treasured rituals. I’m sure you’ll find many pleasant hours in your new hobby.
As for reading, I recommend The Book of Tea by Kakuzo Okakura. It is written by a (slightly biased) Japanese gentleman who wanted to explain to Westerners the importance of the Tea Ceremony (Cha no Yu) to Japanese culture.
Finally, I recommend Hibiki-An for purchasing tea directly from Japan. The tea is the highest quality I’ve ever found, at prices which are actually cheaper than some U.S.-based retailers, and with super-fast shipping. I usually get about $80 worth of tea (free shipping for orders over $38) and I receive it in 4 to 5 days. I keep the tea refrigerated except for the package I am actively using. Drinking everyday, this lasts around 4 months.
The green tea sold in bags is not worth buying, in my opinion. Tea leaves of sufficient quality are packaged as loose leaf or bulk tea. The rest of the leaves (the small bits left over after processing high quality tea) are bagged. The smaller pieces oxidize more quickly and the overall quality of the small bits yields less flavor. Bag tea will often end up brown instead of green. This is because the tea is already oxidized and the flavor is completely ruined. You can sometimes find “bag” tea which is loose leaf tea inside silk satchets. This tea is sometimes quite good, but it depends on how long it has been sitting on the shelf. Buying loose leaf tea and a stainless steel tea ball (easier to clean than the mesh variety) is the best option I’ve found. Loose tea can be stored for longer periods of time because the leaves are larger. Even if the outside oxidizes, the inside still yields good tea. However, I once purchased some sencha that completely surprised me. It looked and smelled very good but when brewed it came out brown and lifeless.
In general, green tea should be packed in air tight foil packages under refrigeration for maximum quality. If you go into a tea shop and there are glass jars with loose tea sitting in them, don’t bother with their green tea. The oolong and black teas are probably fine, but the green tea is almost certainly oxidized and photo-oxidized.