Question for you, is the loose powder better than the pellets?
That is a hard question as I do not know your shooting habits. With pellets you load two pellets or perhaps three if necessary, the projectile and shoot. If all you do is shoot four or five times a year to check the sights, and then once or twice a year hunting to take your game, pellets work great.
If you are someone that wants to shoot a lot. Maybe once a month or so. Or in my case, several times a week, then loose powder is the only way to go.
They both clean up the same.
They both are easy to load. Premeasured loose powder charges in a tube are easier to load then digging into your pellet box IMO, when hunting.
Both produce great accuracy in rifles.
Pellets are expensive, while loose powder is much more cost effective.
Loose powder gives you the opportunity to tinker with powder charges. Try making 87 grain charges with pellets. Although many will tell you, 5 grains here or there makes little difference on the hunting range, and they are probably right.
I can take my scale and weigh out loose powder and have a much more exact load then any other method. It is time consuming, but it is something to do and is fun to see just how accurate you can make your rifle be.
If you plan to shoot a lot on the range and in the field, then go with loose powder. Actually I like it over pellets. But let me add, pellets can really spoil you. If you want to hunt a few extra days a year, maybe a range trip or two, a box of pellets will do you fine.
To store the pellets after opening, I would put them in a kitchen vacuum sealer bag and take the air out of them. No air, no humidity, no fire danger, and no going bad. Then store them in a cool dry place out of the way of children.