XBTS is a decentralized exchange running on top of the BitShares Network. It supports decentralized trading on all popular altcoin pairs without a single point of failure. You always hold the private keys to your funds, only you have access to them.
BitShares is a platform running on Graphene and providing all the necessary tools and features such as Decentralized Verification, Public P2P Network, Industry-Grade Security, DPOS Consensus, Decentralized Decision Making, Stakeholder-Approved Project Funding, Decentralized Exchange, Counterparty-Risk Free Trading, Integrated Payment Solution, Price-Stable Cryptocurrencies, Referral Program, Prediction Markets, and Recurring & Scheduled Payments. XBTS DEX is a BitShares-based decentralized exchange and an entry point into the decentralized market. The XBTS’s user-friendly interface makes this BitShares platform easy to use for anyone.
When you speak about XBTS and Bitshares account, you speak about the same thing. It means that you can create an account at Bitshares.org and log in with it at ex.xbts.io, and vice versa.

As XBTS DEX is a BitShares platform, it is obvious that they have the same registration process and the same account models. XBTS built using the latest in industry research, BitShares 2.0 offers a stack of financial services including exchange and banking on a blockchain.

XBTS runs on of the BitShares Blockchain which is decentralized by DPoS consensus. Decentralization gives XBTS robustness against failure. Users are in control of their own security, which can be much better than any centralized entity. Delegated Proof of Stake (DPOS) is the fastest, most efficient, most decentralized, and most flexible consensus model available. DPOS leverages the power of stakeholder approval voting to resolve consensus issues in a fair and democratic way. Perhaps most importantly, the consensus protocol is designed to protect all participants against unwanted regulatory interference. XBTS DEX is decentralized across the globe. No single point of failure.

XBTS has several different kinds of accounts: Basic Account, Annual Member, and Lifetime Member. Basic Accounts are Free, but do not qualify for the referral program, not any cash back on transaction fees. More information https://ex.xbts.io/#/explorer/fees

SmartCoins provide the freedom of cryptocurrency with the stability of the dollar.

A SmartCoin is a cryptocurrency whose value is pegged to that of another asset, such as the US Dollar or gold. SmartCoins always have 100% or more of their value backed by the BitShares core currency, BTS, to which they can be converted at any time at an exchange rate set by a trustworthy price feed. In all but the most extreme market conditions, SmartCoins are guaranteed to be worth at least their face value (and perhaps more, in some circumstances). Like any other cryptocurrency, SmartCoins are fungible, divisible, and free from any restrictions.