The choice depends specifically on your goals, and how you wish to tailor your metabolism. Though the products work through similar pathways, the GS content in P-Slin leads to a mediation of separate parts of them. Due to this divergence, P-Slin most likely will not produce quite the same cumulative body composition changes, however, more endurance and strength, and vice versa with AP-P-Slin.
The differences between the products are twofold; firstly, GS (whole GS extracts are useless, btw, it's a specific leaf extract) has been shown in clinical trials to raise serum levels of Insulin in both IDDM and NIDDM in rat models. It is hypothesized this comes as a result of regeneration of both the islets and beta cells, often returning pancreatic secretion to normal levels. Obviously, this creates a convergence of glucose to myocytes, but Insulin is not selective, hence the second difference - the direct lipogenesis effect of AP/YG; the constituent of YG, which is included in AP, modulates PPAR Gamma 2 to prevent the binding of blood lipids by accumulated adipocytes.
As well, at least in the clinical trials I have seen, serum levels of Insulin were lowered by the constituent in YG as a response to supraphysiological levels of GLUT4. As I have noted, this might then create a 'fasting' response in adipocytes to further decrease PPAR Gamma 2 (it is lowered in response to fasting).
So, it depends on your goals, if you are only planning on purchasing one product.