>>4283284That's only half true, some are synthetic oxides, some aren't - but you're right that it's kinda strange either way considering that there are synthetic options available.
Like I said, I'm only guessing at the reasons for many of these paints being weak in commercial paint lines.
>>4283251No, other earthtones are also consistent, a lot of them just aren't very good in most brands. Like I said, I'm not actually entirely sure why, it's just a tendency I've noticed overall.
If you want to go with a regular burnt sienna, I recommend looking at some swatches for the brand you're intending to buy from. Jane Blundell's blog is great for that.
On the other hand, transparent red oxide is more saturated which can be good, but also extra work to dull down if you need a more neutral brown, that can be a hassle for beginners especially.
>>4283348 explained the advantages and disadvantages pretty well. 
