Lately Seal boys were also found using DI novosky ar15 and m4 is still most abundant in US specs guys inventory
The use of special equipment by SF is not really an indicator of reliability or superiority. Navy seals still use M60 over M240 because of it's size advantage even though M240 was miles ahead in reliability and ease of maintenance. They also used highly maintenance intensive and failure prone platform like stoner 63. They have higher budgets and better access to spares and replacements.
Noveske N4 and Knight's SR-15 are specialised rifles that US Special forces find convenient. Half the spares are available on depot with M4/M16 lowers lying aplenty. No extra training is required to quartermasters or soldiers themselves. They will take anything that offers supeiority over the vanilla M4 which by now has matured into a reasonably reliable platform despite being DI. Commonality with M4 is incentivised as it makes it easier to maintain their rifles.
The Indian scenario is different. Our budgets are really tight, so even for special forces, the rifles need to be reliable, rugged and affordable. Commonality with existing rifles is not a big deal as we have only a few thousand tavors and M4 to begin with. Hence the affinity for upgraded AKMs which weight close to 5kg loaded without any attachments.
A piston rifle is more likely to find favour over DI in Indian scenario, Sig716 not withstanding. They massively undercut IWI in price, and frankly were a much better option than Galil 52. Further, the overall size / length specs given out for carbine tender (650 mm collapsed, 800 mm extended0 also give advantage to a carbine with folding stock. While a M4 derivative will have to be shorter than 10", a rifle with folding stock, say SiG MCX can make do with 13" barrel and still fit within the upper limits. A 13" barrel will definitely have more controllability and accuracy than a 10" barrel, not to mention lower sound and signature.
There are plenty of good DI rifles and plenty of good piston rifles. SiG MCX was horrible when introduced and now they have perfected it (although the handguard is very flimsy). HK416 were far reliable than M4 when introduced but the competition in DI has caught up big time, not to mention the weight advantage. SCAR is both overpriced and heavy due to it's bulky polymer body reinforced with steel on moving surfaces and has not delivered on the modularity promised in the beginning. SiG is really gunning for major military contracts like NGSW and Indian Army procurement. If they play it right, they will have two of the largest clients in the free world and from the looks of it, they will be very aggressive going forward.