Experts say both of these words originated from the word 'Sin'dhu' (सिन्धु). Even the word 'India' originated from this word!
Lots of upper and middle class Hinđū/s tend to choose English over Hinđī!
Sanskṛiŧ was the language of Brāhmaṇ/s (ब्राह्मण), a section of so called upper caste Hinđū/s.
Prākṛiŧ/s (and Apabhran'sha) were the languages spoken by masses in Ancient India! These languages along with Sanskṛiŧ are the roots of Hinđī.
Other Indic languages are also descendants of Sanskṛiŧ (the refined and sacred language) and Prākṛiŧ/s (प्राकृत, unrefined dialects).
Lots of words in Hinđī were also taken from South-Indian languages, An'grejī (अंग्रेजी, English), Fārasī (फ़ारसी, Persian), Arabī (अरबी, Arabic), Ŧurkī (तुर्की, Turkish) and Purŧagālī (पुर्तगाली, Portuguese).
A lot of Hinđū/s speak 'Hinđī', but lots of Hinđū/s speak other languages as well. A lot of indians following religions which are similar to Hinđūism speak either Hinđī or its dialects. E.g. some Indian Buđđhists (बुद्धिस्ट; बौद्ध, Bauđđha/s).
People of a business community called Māravāḍī (मारवाड़ी) used to speak a dialect of Hinđī. Now they mostly speak Hinđī. For lots of them, their community matters a lot!
Other Hinđū communities like Gujarāŧī (गुजराती), Sinđhī (सिन्घी), ... which are influential in business and trade speak their native languages along with Hinđī. Thus Hinđī is the main language of business in the South Asia (Eshiā)!
Some businessmen speak their native languages/dialects when they don't want their customers to understand what they are talking about.
Business communities (tribes) keep looking for ways to exploit ordinary customers. Be careful of those who have very strong bindings with their communities. Persons belonging to these communities sometimes behaves like royalties. Beware of befriending such persons; you may end up exploited.
Hinđī is spoken mainly by people living in central India (Mađhya-Prađesh; मध्य-प्रदेश) and in lots of northern states, namely Delhi (NCR; Đillī; दिल्ली), Uŧŧar-Prađesh (उत्तर-प्रदेश), Bihār (बिहार; मगध), Haryana (Hariyāṇā; हरियाणा), Rājasŧhān (राजस्थान), Uŧŧarākhan'd (उत्तराखंड), Himāchal (हिमाचल). Hinđī is also spoken in parts of Chhattisgarh (Chhaŧŧisagaḍh; छत्तीसगढ़; दक्षिण-कौशल), Jharkhand (Jhārakhan'd; झारखंड) and Maharashtra (Mahārāṣhtra; महाराष्ट्र).
In the state of Punjab (Pan'jāb), Hinđī co-exists with Pan'jābī (पंजाबी) which is similar to Hinđī.
Marāthī (मराठी) and Gujarāŧī (गुजराती) are the main languages of the western India. The Marāthī and Gujarāŧī speaking people can also speak Hinđī. Hinđī entertainment industry is in Mumbai (Mum'baEE). Lots of people of Eastern & South-East India (mainly Ānđhra-Prađesh; आंध्र-प्रदेश) can also speak Hinđī albeit with some accent.
Outside India, Hinđī is one of the main languages of Mauritius (मॉरिशस; Maurishas), Fijī (फ़िजी), Trinidād (त्रिनिदाद; ट्रिनिडाड और टोबैगो), Guyānā (गयाना या गुयाना), ...
Lot of influencial Indians and some of those people who have to speak Hinđī (because it is a link language), secretely dislike it!
अधिकतर फिल्मी कलाकार, निर्देशक आदि जो हिन्दी की खाते हैं, वो भी अंग्रेजी बघारते हैं।
India is divided along/by languages. So some ugly politicians and partisans try to make people of their constituencies hate Hinđī. E.g. radicals in Ŧāmil-nādu and Keral, petty politicians of Mahārāṣhtra and insurgents in some parts of Ban'gāl (Bengal), Asam (Assam; Āsām) and other eastern states. They want to divide public over languages, religions, castes etc.
I appeal to Hinđī speaking people to try at least one other Indian language. That is easy as the roots are same. See how easily other Indians pick-up and speak Hinđī.
The Muslims in South Asiā speak a language similar to 'Hinđī', but prefer to call it 'Urđū'. The grammar of 'Urđū' is almost like that of 'Hinđī'.
Some Muslims try hard to include more and more Persian (फ़ारसी, Fārasī) and Arabic (अरबी, Arabī) words and avoid using words with Sanskṛiŧ roots.
Some writers and poets use those words and phrases which public don't understand!
Some Hinđī-purists also try to use rare words with Sanskṛiŧ roots and avoid using common words with foreign roots.
The word Hinglish can be used to refer to the language of a section of society who live mainly in metros or big cities. Some of these people use Hinđī to refer to inferior things (shame on them) and things related to masses.