I like turn based best, but I enjoy both. I'll also respond to each of your reasons.
In a well balanced turn based RPG, the game can prove difficult, but still be possible to complete without requiring the player to grind. There are many games that do this, and they still have difficulty without the impossible without grinding difficulty.
Being easier to understand and master as a action RPG and turn based RPG isn't correct. An action RPG can have gameplay ideas that are more difficult to use than a turn based RPG. Take Oblivion for instance. One well known issue about the game is the level up system. In order level up properly and get stronger, you need to get the 10th level in your major skills right when or after you have 10 points in three different categories. Does that not sound confusing to you? When the game doesn't even tell you that and the gamer is supposed to find out themselves it makes it worse. There's also binding weapons, binding armor, creating spells, etc. There's quite a bit of depth to the game that you won't be able to do and when you can do it there's just a lot going on. And I've only described some of what the game has to offer.
No random encounters is actually a much worse way an RPG can be played and can make a game too easy or too hard. Borderlands is an action RPG and if you want to do even a reasonable amount of quests, because of there being no random encounters, the game starts to become way too easy. I'm talking about one or two hits with a pistol killing enemies, etc, damage against the player, even where you're supposed to be at being 1HP per hit, etc. I quit playing the game because as easy as it was no fun.
The other thing about no random encounters is that the player has the option to dodge these enemies or kill everything that comes across the player. The only way to actually make it balanced, is to require the amount of enemies to be killed is all of those you come across, so get into every single battle. But what if the player on his own feels that he doesn't want to fight the enemies and dodges a good portion of them and later becomes too weak? Random battles actually force you to get into battles within a certain amount of steps, and again, correct balancing, will make it not get too easy or impossible without grinding.
Action based combat can be satisfying as can a turn based title, it can be tedious in an action RPG as it can be in a turn based title. It's just how the game is developed.
Level doesn't hinder as much as a turn based game. See my above post about Borderlands. Or see Oblivion if you don't level up properly, or take Skyrim for instance. Skyrim as an action RPG has horrible balancing. Human like enemies and dragons are easy on adept difficulty, but mammoths and ogres can one shot you, while others like the sabertooth might be 50/50 on whether you win or lose. Increasing difficulty by one human like enemies and dragons are now decent difficulty, but easily killed, you'll still get one shotted by mammoths and ogres, and sabertooth and other more powerful wild creatures will also kill you. Again, it's all based on the game.
Basically, towards most reasons why you like action over turn based, as I've stated in many of them. It's all on a per game basis. I could point out comparisons on games that have excellent balance that remain difficult while still being possible to complete without any grinding whatsoever both action and turn based. I could also do the same and point out games that you have to do a ridiculous amount of grinding in order to proceed, also on both action and turn based.
