Which one do you think is more challenging: Sales or Customer Service?

It's the same challenge.
In sales you need to have the customer service parts.
Also in customer service you need to have the sales parts.
If you're a sales man, You need to know very well how to deal with all kinds of human beings, And that's the same on customer service.
The two position need a Powerful, Clever, Quick-witted and a person who can handle the hard situations.

two different things! customer care is tricky cause it's as it is "taking care of an existing client/customer" sales on the other hand is "convincing a prospect to become a client/customer"

Both are connected and challenging and stressful

Raising the sense of need and properly introducing the value of any product could help selling a product.
In the process of selling something the quality of product, strength of brand and marketing plan of a company works together, so a salesperson works on an already provided base.
But when an angry or unsatisfied customer comes back with lots of complains and frustrations, that time we could really test the quality of intelligent staff and customer support personnel.
In my opinion selling something is much easier than providing top of the line customer support and service.
This is the Customer Services department which make the path of sales team smoother and easier.

In my opinion customer service is always the foundation, without a proper customer service repeat purchases become impossible, furthermore, word of mouth remains the no.
1 marketing tool ever existed and if your consumers are not happy with your after sales services, you will get word of mouth but unfortunately on the opposite direction.

I believe that two positions are inseparatable, yet customer service is a little bit broader.
Customer Service Officer is also a sales man who sell products of a bank for instance.
He should have selling skills along with customer service orientation.

There is a direct proportionality between Sales & Customer Service we always see in almost all sort of the businesses.
In my opinion, Sales is a very tough task for some commodities around the world, but for some products which are not FMCGS (Fast Moving Consumer Goods) Customer Service would definitley be vital and should have upper edge over Sales.
It's easy to purchase COKE from a shop as we never negotiate with the sales person of that store for price and affordability, but we definitely be more specific, if we would engage in the purchasing of a Celluler Phone from Nokia Store, we would negotiate with the sales person for some better hand set under affordability and also re-visit that store for WARRANTY (total activity of Customer Service Manager) if any thing went wrong with the handset.

The client is very important That means that the most important customer service Through the ideal customer service are required to achieve sales But access to achieve the highest sales

I agree with Ms Nadia Ahmed Mohammed Saeed

Dear Mr.Muhammed In my opinion sales, marketing and customer service has the same challenges because they are dealing with humans and human psychology is the most complicated and sophisticated science in the world however I can say that sales people are luckier because when they overcome their challenge and sell they get their award instantly in the shape of commission but the customer service people get this award in another shape which is customer appreciation in the end of the process

No one till you got this when you have competitions with other services.
then both are challenges.