It should be noted that AVRs still come in PDIP28 even today. The smaller form factors (6-pin, 8-pin, or 14-pin) are surface-mount only though.
Still, if your main goal is PDIP or through-hole form factor, I recommend buying the PDIP28 versions of these chips where possible.
I use these little adapter boards for breadboard prototyping. I don't keep DIPs around anymore because I don't use them. I have ZIF to DIP adapters for most of the chips for orgasming but for breadboard development I find these little boards work just fine.
The main issue with those adapter boards is that an entire custom PCB is like $7 these days (albeit you need to order multiple copies, plus shipping...). But lets say a 4x copies of some custom PCB costs ya $35 after shipping.
That's an American manufacturer too: Digikey Red. Other parts of the world can be cheaper depending on shipping costs.
So spending $3 to $5 on these little converter boards feels... weird (plus shipping)? If going for prototyping purposes, spending $2.50 on a 28-pin PDIP28 that you can just plop-down onto a breadboard or whatever is probably better?
I do miss the 8-pin PDIPs. I know the older chips (ATMega328) used to come in smaller 8-pin or 14-pin PDIP forms, but Microchip's newer chips are PDIP28 only.
Prototyping is important. The main benefit is getting a prototype done ASAP to iterate on your designs. But is it too difficult to switch from 28-pin prototypes to 14-pin final products? (Ex: AVR32dd28 PDIP-28 for prototyping, then switch to the AVR32DD14 SOIC-14 for the final custom pcb design?)
