I am comparing Illustrator text selection to that of Affinity Designer 1.3.2. In Illustrator, if I have multiple text boxes present on the page, I need only choose the Type Tool and the pointer changes to an I-beam, and when I mover that point over any text box, the box highlights with a blue underline. I can then click and drag to select text. And once text is selected that way in one box, I need only do the same thing to select text in another text box. No double-clicking or special text insertion tricks required. No so with Affinity Designer though.
In Affinity Designer, if I click the Artistic Text Tool and hover over any text boxes on the page, none of the text highlights. Furthermore, if I try to just click-and-drag atop any text box, AD creates a new text box rather than highlighting text in the existing box! I am forced to double-click to insert the text cursor inside an existing text box in AD. And once there, I cannot simply click-and-drag on another text box to select it. I must go to the trouble of double-clicking to insert the text cursor in other text boxes.
It may not sound like much, but this time waster is a huge time waster when you deal with a lot of text editing like me.
One more thing. There is a small but noticeable lag when it comes to selecting a lot of text by click-and-drag and even typing text. It feels on order of 200ms or so for text selection, and less than that for typing text. I feel no lag at all when selecting text by click-and-drag or tying text in Illustrator though. This is true in an existing document as well as in a new document.