Differences between Vaikuntha loka and Goloka.
According to many Vaishnava scriptures Goloka Vrindavan is the eternal abode of Lord Krishna whereas various Vishnu forms reside on the Vaikuntha planets. Both of these exist in the spiritual universe beyond the highest Lokas of our material Universe.
As Lord Narayan tells Narad muni in the Devi Bhagvatam:
Nârâyana spoke :-- “O Devarsi! The Mûlâ Prakriti, of the nature of Mâyâ of Para Brahman is an eternal entity (the nabho mandal); Time (Kâla), the ten quarters, the Universe Egg, the Goloka and, lower than this, the Vaikuntha Dhâma all are eternal things. Âtman and Prakriti are in inseparable union with each other as Fire and its burning capacity, the Moon and her beauty, the lotus and its splendour, the Sun and his rays are inseparably united with each other.
Lord Krishna also tells Arjun in the Mokshadharma Parva of the Mahabharat:
"The blessed and holy one continued. 'Having mutually caused such marks on each other's person, the two Rishis Nara and Narayana thus made friends with Rudra. and dismissing the deities, once more set themselves to the practice of penances with a tranquil soul. I have thus told thee, O son of Pritha, how in that battle which took place in days of yore between Rudra and Narayana, the latter got the victory. I have also told thee the many secret names by which Narayana is called and what the significations are, O Bharata, of one of those names, which, as I have told thee, the Rishis, have bestowed upon the great God. In this way, O son of Kunti, assuming diverse forms do I rove at will through the Earth, the region of Brahma himself, and that other high and eternal region of felicity called Goloka.
Some scholars are also of the opinion that even the Rig Veda hints at this place in the hymn to Vishnu:
5 May I attain to that his well-loved mansion where men devoted to the Gods are happy. For there springs, close akin to the Wide-Strider, the well of meath in Viṣṇu's highest footstep.
6 Fain would we go unto your dwelling-places where there are many-horned and nimble oxen, For mightily, there, shineth down upon us the widely-striding Bull's sublimest mansion.
That the Goloka is the abode of Krishna is also mentioned in the Brahma Samhita.
The super excellent station of Kṛṣṇa, called Gokula has thousands of petals and a corolla like that of a lotus sprouted from a part of His infinitary aspect, the whorl of the leaves being the actual abode of Kṛṣṇa.
Although this particular verse mentions Gokula it actually refers to Goloka as would be evident from other verses which give much more detailed description about this abode here. The Harivansha which is considered a sort of extension to the Mahabharat, also mentions:
apAmadhastAlloko vai tasyopari mahIdharAH | nAgAnAmupariShTAdbhUH pR^ithivyupari mAnuShAH ||2-19-26
Water is at the lowest level. Above water, there are mountains. Earth is on mountains and people live on earth.
manuShyalokAdUrdhvaM tu khagANAM gatiruchyate | AkAshasyopari ravirdvAraM svargasya bhAnumAn ||2-19-27
It is said that the world of birds (sky) is above the world of people. Above the sky is the sun The sun with rays is the entrance of heaven.
devalokaH parastasmAdvimAnagamano mahAn | yatrAhaM kR^iShNa devAnAmaindre vinihitaH pade ||2-19-28
Above this is the great world of deva-s, which can be reached by vimAna. kR^iShNa, I am installed there at the position of indra among deva-s.
svargAdUrdhvaM brahmaloko brahmarShigaNasevitaH | tatra somagatishchaiva jyotiShAM cha mahAtmanAm ||2-19-29
Above heaven, is the world of brahma, served by the group of brahmarShi-s. The moon and the planets move there.
tasyopari gavAM lokaH sAdhyAstaM pAlayanti hi | sa hi sarvagataH kR^iShNa mahAkAshagato mahAn ||2-19-30
Above this is the goloka, governed by sAdhya-s. That great world, kR^iShNa, pervading the great sky all over, is above all worlds.
Coming to the relative positions of Goloka and Vaikuntha, another section of the Devi Bhagvat Puran says:
Each Brahmânda extends from Pâtâla to the Brahmâloka. The abode of Vaikuntha is higher than that (i. e. it is situated outside of Brahmânda), again the abode of Goloka is fifty koti yojanas (50 x 10 x 4 x 2 million miles) higher than Vaikuntha. This Goloka Dhâma is eternal and real as S’ri Krisna is eternal and real.
The same is corroborated by the Shiv Purana:
Jana loka is situated above Mahaloka where as the Tapaloka is situated at a distance of twenty six lakh yojans above Mahaloka. Satyaloka is situated six times the distance between Mahaloka and Tapaloka. Satyaloka is also known as Brahmaloka. Beyond Brahmaloka is situated the Vaikuntha loka. Similarly the world of Kartikeya Kumar loka is situated beyond Vaikunth loka. After Kumar loka comes the Uma loka and then comes the Shiva loka, which is the farthest loka. Goloka is situated near Shivaloka where lord Krishna lives with the cow names Sushila, with the permission of lord Shiva.
Although the Shaiva texts say that Krishna lives there at the behest of Lord Shiva still they concur with the Vaishnav texts that Goloka is at the highest level and is certainly higher than the Vaikuntha.
To conclude, Goloka Vrindavan is the highest abode where Lord Krishna resides while the Vaikunthas are relatively lower in position and that is where the various Vishnu forms reside.