Here's why we need a wall, not "massive security" on the border...

A wall of drones, virtual sensors or border agents could be cancelled on day 1 of a new Democratic Presidency. Also, it would require new funding every year. If we can always have a Republican President who values border security and a GOP controlled Congress, maybe it would be OK. Can you guarantee that? A significant physical wall would require funding from Congress to tear down. Even a minority GOP could likely obstruct that. Albeit, if democrats held power for a long time, they could degrade a wall by letting it fall into disrepair.

One other problem with not having a physical barrier is it allows illegal immigrants to step onto US soil before they are apprehended. Then, they can claim refugee status (say they fear for their safety in home country) and we have to give them a hearing before an immigration judge. If Democrats were in charge, this would be mostly liberal judges. Obama found a way to go around even this minor inconvenience to illegal immigrants. Instead of taking them into custody until the hearing, he had the Border Patrol issue the illegal immigrants summons and then turn the loose into the US. Of course, up to 90% failed to show up for their immigration hearing.

Nothing but a significant physical structure will work long-term. Democrats and the GOPe know this. That's why they oppose it.

Yes. Trump can make Mexico pay for the wall and it will be easy

A 10% tax on immigrant remittances would do it.

Yes, you read that correctly. Immigrant remittances received by Mexico have surpassed Mexico’s $23.4 billion in oil earnings. This means the government of Mexico is more dependent than ever on the earnings of maids and gardeners in the U.S. to keep itself afloat. This is the leverage Donald Trump talks about to pressure Mexico to pay for the border wall.
Trump’s proposal carries: the border wall solution, the employment solution, the enforcement mechanisms of current law, and another angle that is strategically essential. “WESTERN UNION REMITTANCES” (Money Services Compliance)

Obama criticizes Trump's idea of building a wall on the border

Obama still likes the fence around the White House, doesn't he? 

Via Daily Caller:

President Barack Obama took an implied swipe at Donald Trump’s desire to build a wall along the U.S./Mexico border during a speech Monday at the United Nations General Assembly.
“We see greater polarization, more frequent gridlock, movements on the far right, and sometimes the left, that insist on stopping the trade that binds our fates to other nations, calling for the building of walls to keep out the immigrants,” Obama said.
“Most ominously we see the fears of ordinary people being exploited through appeals to sectarianism, or tribalism, or racism, or anti-Semitism,” he continued.
“Appeals to a glorious past before the body politic was infected by those who look different or worshiped God differently,” he said. “A politics of us versus them. The United States is not immune from this.”