They give these reasons for that conclusion: Pfizer probably has more room to raise its offer and win over AstraZeneca shareholders, a rival bid for the British firm is unlikely, the deal is unlikely to face any major regulatory hurdles and a weak earnings backdrop is an incentive for Pfizer to push for a deal now.
"Pfizer has historically been aggressive at pursing mega-mergers when it considers it the right time," Raghuram Selvaraju, head of healthcare equity research at Aegis Capital, told CNBC Asia's "Run Down."
"We think this upcoming merger with AstraZeneca could be Pfizer's easiest takeover yet, mainly because it is primarily motivated by taxes and Pfizer is trying to escape U.S. taxes and get into the U.K. tax system which will yield significant profits for shareholders form the combined companies," he said.
According to Selvaraju, Pfizer currently has a tax rate of about 27 percent in the U.S. and it would pay a rate of about 10 percent on profits generated on UK-based patents.
"Pfizer won't reveal what the blended tax rate would be but obviously we can expect it to be below the 27 percent it currently pays," Selvaraju said.
Pfizer on Friday raised its initial cash and stock offer to just over $106 billion from $99 billion in its third attempt to win over AstraZeneca. AstraZeneca's board rejected the latest bid just hours after it was received, saying the offer was too low.
Selvaraju said he expects that Pfizer could probably up its offer to the $110-120 billion range without any serious problem.
If the merger goes through, it would be the largest acquisition of a British company by a foreign business.
Pfizer on Monday said its total first-quarter revenue fell 9 percent to $11.35 billion, which was $730 million below Wall Street expectations, on falling sales for generic drugs and highlighting its interest to pursue AstraZeneca to promote business growth.
"We are rather skeptical about the company's optimism that all is going well. And we consider the bid for AstraZeneca as plan B rather than plan A," Sam Isaly, founder and managing partner at OrbiMed Advisors, which holds shares in Pfizer, told CNBC's "Fast Money."
"The bid for AstraZeneca is a good bid and we think it will succeed. AstraZeneca is putting up a fight but we think Pfizer will prevail and the shareholders want a higher price," he said.
David Williamson, a healthcare analyst at Motley Fool told CNBC, that AstraZeneca was a company that would fit in well with Pfizer's business units and bolster its established products division.
"AstraZeneca has some interesting stuff in immuno-oncology, which is going to be a growth area. So adding that is very attractive to Pfizer in the long-term," he said.
"I don't think Pfizer is going away. I don't think there will be a bidding war either," he said. "AstraZeneca has hasn't had much interest in this and the management has been stubborn. If they push Pfizer away and blow the deal then these shares are going to come back down."
AstraZeneca shares are up about 35 percent so far this year.