Here is some thirty-year-old research that still seems relevant today:
Richard E. Clark, 1983, "Reconsidering Research on Learning from Media", Review of Educational Research, Vol. 53, No. 4 (Winter, 1983), pp. 445-459.
This paper reviews the the seemingly endless research trying to ask whether teaching using Media X inherrently more effective than the same instruction in Media Y. Given the age of the paper, you will not suprised to learn that the research cited covers media like Radio for education (hot research topic in the 1950s), Television (1960s) and early computer-assessted assessment (1970s). Clark's earliest citation, however, is "since Thorndike (1912) recommended pictures as a labor saving device in instruction." Images as novel educational technology! Well, they were once. The point is that basically the same reserach was done for each new media to come along, and it was all equally inconclusive.
Here are some choice quotes that nicely summarise the article:
Based on this consistent evidence, it seems reasonable to advise strongly against future media comparison research. Five decades of research suggest that there are no learning benefits to be gained from employing different media in instruction, regardless of their obviously attractive features or advertised superiority.
Where learning benefits are at issue, therefore, it is the method, aptitude, and task variables of instruction that should be investigated.
The best current evidence is that media are mere vehicles that deliver instruction but do not influence student achievement any more than the truck that delivers our groceries causes changes in our nutrition
Clark does not miss out on the fact that effectiveness of the learning is the only problem in education:
Of course there are instructional problems other than learning that may be influenced by media (e.g., costs, distribution, the adequacy of different vehicles to carry different symbol systems, equity of access to instruction).
Since this paper is a thorough review of a lot of the available literature, it contains a number of other gems. For example:
Ksobiech (1976) told 60 undergraduates that televised and textual lessons were to be (a) evaluated, (b) entertainment, or (c) the subject of a test. The test group performed best on a subsequent test with the evaluation group scoring next best and the entertainment group demonstrating the poorest performance.
Hess and Tenezakis (1973) ... Among a number of interesting findings was an unanticipated attribution of more fairness to the computer than to the teacher.
I wonder how much later research fell it to the trap outlined in this paper. I am not familiar enough with the literature, but presumably there was lots of papers about the world-wide web, VLEs, social media, mobiles and tablets for education. I wonder how novel they really were?
Today, computers and the internet have made media cheaper to produce and more readily accessible than ever before. This removes many constraints on the instructional techniques available, but what this old paper is reminding us is that when it comes to teaching, it is not the media that matters, but the instructional design.