The fasts followed today are somewhat different from those mentioned in the earliest scriptures of Hinduism so I would share what the older scriptures mention about them. The Law Books such as the Manusmriti prescribe elaborate rules and procedures to practice fasting which may either be done to gain some spiritual merit or as a means for atonement.
"Angiras said, 'As regards Brahmanas and Kshatriyas, fasts for three nights at a stretch are ordained for them, O delighter of the Kurus. Indeed, O chief of men, a fast for one night, for two nights, and for three nights, may be observed by them. (They should never go beyond three nights).
As regards Vaisyas and Sudras, the duration of fasts prescribed for them is a single night. If, from folly, they observe fasts for two or three nights, such fasts never lead to their advancement. Indeed, for Vaisyas and Sudras, fasts for two nights have been ordained (on certain special occasions). Fasts for three nights, however, have not been laid down for them by persons conversant with and observant of duties.
That man of wisdom who, with his senses and soul under control, O Bharata, fasts, by abstaining from one of the two meals, on the fifth and the sixth days of the moon as also on the day of the full moon, becomes endured with forgiveness and beauty of person and conversance with the scriptures. Such a person never becomes childless and poor.
He who observes fasts on the eighth and the fourteenth days of the dark fortnight, becomes freed from maladies of every kind and possessed of great energy.
The man who abstains from one meal every day throughout the month called Margasirsha, should, with reverence and devotion, feed a number of Brahmanas.
That man, O son of Kunti, who passes the whole month of Pausha, abstaining every day from one of two meals, becomes endued with good fortune and agreeable features and great fame.
He who passes the whole month of Magha, abstaining every day from one of the two meals, takes birth in a high family and attains to a position of eminence among his kinsmen.
He who passes the whole month of Bhagadaivata, confining himself every day to only one meal becomes a favourite with women who, indeed, readily own his sway.
He who passes the whole of the month of Chaitra, confining himself every day to one meal, takes birth in a high family and becomes rich in gold, gems, and pearls.
The person, whether male or female, who passes the month of Vaisakha, confining himself or herself every day to one meal, and keeping his or her senses under control, succeeds in attaining to a position of eminence among kinsmen.
The person who passes the month of Jyaishtha confining himself every day to one meal a day, succeeds in attaining to a position of eminence and great wealth. If a woman, she reaps the same reward.
He who passes the month of Ashadha confining himself to one meal a day and with senses steadily concentrated upon his duties, becomes possessed of much corn, great wealth, and a large progeny.
He who passes the month of Sravana, confining himself to one meal a day, receives the honours of Abhisheka wherever he may happen to reside, and attains to a position of eminence among kinsmen whom he supports.
That man who confines himself to only one meal a day for the whole month of Proshthapada, becomes endued with great wealth and attains, to swelling and durable affluence.
The man who passes the month of Aswin, confining himself to one meal a day, becomes pure in soul and body, possessed of animals and vehicles in abundance, and a large progeny.
He who passes the month of Kartika, confining himself to one meal every day, becomes possessed of heroism, many spouses, and great fame.
So to answer your questions different types of fasting give different types of benefits and one should choose them based on what he/she wants to obtain by performing the fast.