Both the bikes are priced at the same category but Dahon's price has gone down quite a bit since a few years. They used to cost more, just check the prices in Singapore which is priced much higher than ours. Both are quality bikes but the Tern Link D8 is the least expensive model from Tern while Dahons have even cheaper models. I can't really give a real opinion as I am more inclined to the Dahons as my wife and daughter, in addition to myself ride Dahons.

The speed P8 is almost complete, meaning the hubs are cassette type (you can upgrade to 9 speed later by just buying a cassette, RD and shifter), the handle post can be adjusted, double walled Kinetix rims and the best part is the hand pump encased in the seat post!   It is shodded with a good tyre, in short, it is complete.

Another consideration is, I also have an Eco C7 which is half the price of the Speed 8. After upgrading to 8 speed cassette, change to Deore RD and shifters, it also rides just as well. Need to change the saddle though, the Eco C7 has lousy saddle.

Most importantly, I think is to get up on the bikes and feel the ride position. If the shop allows you to cycle around, even much better but I doubt they will allow though. Buy the one that you feel more comfortable riding in. I too have been scouting in the forums for bargains and narrowed down to two shops in Dengkil which still sells the cheapest. Those air-conditioned bikes shops in PJ/D'sara area are expensive. Check out the shop in Dengkil. 

P/S. Check this site for online bike shop in Korea. Not to buy your bikes here but the availability of Dahon parts compared to Terns. Almost any part can be found for Dahons! 
http://www.bicyclehero.com/us/mountain-roa...ol-commute.html

any lerun dealer can get dahon, just check the lerun dealer website.
frank foo in dengkil got dahon tern lerun i think.

You should try uptown damansara Joo Ngan and son, just next to Village Park Nasi Lemak... Just got my Dahon boardwalk D8 from there on thursday

Bro

Got the address?