I…believe that very important gains in clarity and fruitfulness are to be had from the introduction of such formally constructed languages. This is a difference of opinion which, despite the fact that it does not concern (in my own terms) a matter with cognitive content, is nonetheless in principle susceptible of a kind of rational resolution. In my view, both programs - mine of formalized languages, Quine's of a more freeflowing and casual use of language - ought to be pursued; and I think that if Quine and I could live, say, for two hundred years, it would be possible at the end of that time for us to agree on which of the two programs had proved more successful.-- Carnap (1951) as reported by Howard Stein (1992) “Was Carnap Entirely Wrong, After All?” Synthese.
We're only about one third of the way of Carnap's proposed time-frame to evaluate the fruitfulness of the alternative research programs advocated by Quine and Carnap. So, it may be too early to tell, but it may be useful enough to invite progress reports. Here I leave aside the complex interpretive-philosophical issue to what degree Carnap and Quine really agree about each other's characterizations of each other's and their own projects. In particular, it is by no means obvious that the respective metrics for success are really shared. (Quine may like clarity and fruitfulness, too, but he also likes simplicity and continuity with tradition a lot, etc.).
As an aside, I think it's possible that in the 1970s, or so, it would have looked that Quine's program was winning. One striking, and exciting, feature of the more contemporary scene is that the Carnapian program has been revived (especially in Europe). In fact, I am inclined to think that the two programs have started to generate hybrids. (Some other time I'll discuss evidence for this claim, but lots of formal philosophers in Carnap's sense are also are happy to engage with naturalizing projects in constructive ways, and naturalistic philosophers may happily avail themselves to formal tools.) I am not claiming there are is full hybridization; obviously there are interesting tensions between, say, formal philosophers of science and those that have taken the practice turn.
I am fascinated by the fact that Carnap -- if he is reported accurately by Stein (his student)* -- would allow a 'rational resolution' for something that is in a sense a question without cognitive content (that is, I think, because it is for him an external question--one that involves optative commitments). The particular resolution he proposes suggests, in fact, that he may be writing, in part, for posteriority or has a kind of historical sense of his own enterprise. Again, leaving aside the specific criteria, this rational resolution would be consequentialist. (I am treating 'successful' as consequentialist.) This is no surprise, of course, because his version of the principle of tolerance also has a consequentialist flavor.
Of course, it is quite natural for a scientific philosopher to conceive of (and sell) her own project in terms of a progressive research program. From this vantage point not all consequences are equal. In particular, it's those consequences that track or instantiate some privileged set of scientific virtues that are supposed to trump other consequences. So, for example, that a research program is popular among policy-makers (and only among policy-makers) is not the right sort of consequence from the vantage point of a 'rational resolution' (although certainly it may be useful in other respects if one is looking for jobs). This is not to deny that expected social utility may well be one of the legitimate consequences to evaluate a research program in scientific philosophy, but qua philosophers or truth-seekers we may also think that some non-social consequence may also be very important.
Now, one more thought. Obviously, one may well have a preference for one philosophical research program over another that are based on less consequentialist reasons, and more intrinsic preferences (reasons, virtues, etc.). One sometimes hears scientific philosophers mutter that they are the Enlightenment party (and wink at the vices of Heideggerianism) not just because they think this is beneficial, but also because it is more virtuous or simply more humane (rational, noble, etc.). The most ambitious attempt that I am familiar with this that explores this line of thought (Carnapian philosophy as Enlightenment philosophy) is Carus's book on Carnap: Carnap and Twentieth-Century Thought: Explication as Enlightenment. This book relates Enlightenment to the notion of progress (of which I am a bit suspicious), while holding on to a robust notion of pluralism (which I like). (See Alan Richardson's review for a critical discussion of the use of 'Enlightenment.') But, of course, within the Enlightenment camp there is fierce disagreement over what the right way of doing philosophy is; it's contested. So, an appeal to Enlightenment values will not deliver straightforward metrics of success.
*Full disclosure: Stein was one of my teachers (recall).