Is there any risk of using the cheaper ones? Or is there any benefit using the more expensive ones?
Vietnam now has an eVisa system, so an approval letter is no longer needed. These sites are either scams or simply outdated. The fee is $25 USD. Anyone that charges more or less is a scam. Here is the official page as they must either find another fee to add (or not deliver anothing) or they pocket the difference. Note that official sites are on
.govt.vn (as the first link you sent).
If you are eligible for E-visa, you should apply this kind of visa. It costs 25 USD and has these features: - 30 days of stay - single entry - Be eligible for 46 countries - Can enter through 28 ports (included airports, seaports and land borders) - Apply through Vietnam government website
If you are not eligible for E-visa, you should apply Visa on arrival. It costs from 6 - 50 USD (depend on how long you stay, how many time you enter and which agency you apply with)
My recommended agency: Vietnam-evisa.com (it costs 6 USD for approval letter for 1 month single tourist visa. They processing time said that 2 working days, but I received within 1 day)
Most likely one site (the cheap one) is the genuine one, and the expensive one charges you lots of money to send your details to the original one.
From my experience a Turkish e-visa is $20 and the two first sites on google search try to charge $65 and $89.
The only benefit of paying more is that you keep some scammer happy.