I do trades with Gaspode fairly often - usually customising supplies for customising supplies - but I did a trade with Hathorcat recently which was just amazing.
I had a hair barrette (OK, it's a super duper rare one - Dutch Candys I think?) and she acquired Red Roses, Nightglider, Daisy Dreams and Sweetie Swirl to trade with me.
Usually though I'm not one for letting anything go so trades tend to be out of the question.
Best trade ever
To be honest I wouldn't say I had more luck with one thing over the other because I have had great transactions for both. For expensive, sought after ponies, I have mostly had to purchase those. However, for super rare items - like certain merch or accessories - which are rarer than the super expensive ponies but which hold less value due to them not being sought after by everyone - I have had better luck trading. The example Daffy quotes is one but I have also traded Munchy for a rare barrette and once and an Oakly for 4 adventure cards. Seriously people when it comes to accessories I am a fool I tell you for what I will trade
All in I enjoy a trade more - its more fun putting together a parcel and getting a special box in return - it adds a little story, a little extra to the pony or the item