[JaM]

Merkava Mk3 is complete new tank.But even Merkava Mk1 had better design than Abrams for purposes that israel needs.Abrams is grat tank for WW3 war, but it is not as good as merkava in golan or sinai.Both tanks were build with experience from 1973 Yom Kippur war in mind, but M1 Abrams was much more attack tank and Merkava was suposed to defend.M1 has superior mobility, same firepower and standard protection against KE and good against CE. Merkava Mk1 had very good frontal protection (front turret was quite strong,unpenetrable for late 70s early 80s APFSDS direct hit).Engine in front made Front hull unpenetrable for all CE weapons of late 70s and early 80s,due to compromising mobility.
Merkava Mk4 has most modern passive armor.If you look at Leopard 2A6 front turret addon armor rised protection from 650-700mm KE to 950-1100mm KE.But this layout is 10 years old(2A5)Merkava mk4 has layout from year 2000, so there must be adleast minor improvement in technology.
Biggest weakness of Abrams (in early 80s it wasnt weakness but strongpoint...) is glacis armor. 83° degree is enogh for deflecting all non-precise HEAT warheads and sheated APFSDS rounds, but it is not enough now. Most ATGMs have not problems with it.Even RPG-29 could easily penetrate it.All modern APFSDS will penetrate it from quite great range (BM-42M could do 600mm at 2000m...)
Merkava Mk4 could face Egyptian M1A1 tanks armed with KEW-A1 APFSDS (590mm at 2000m)or new KEW-A2 (660mm at 2000m), so its front hull and turret could handle it. Autotracker and Firecontrol system gives quite good bonus against M1A1.(Same thing works against Jordanian Challengers)