When are R6 objects more efficient than traditional lists?

Question

I am working on an R package where performance is important (there will be many iterations due to bootstrapping), and planned to use the R6 library since an object-oriented approach made most sense in my head. The alternative seems to be "semi-objects" made from lists. But the former seems slower than the latter, even when portable = FALSE and class = FALSE.

Are there ways to speed up R6? Or is lists the way to go?

Here is a simple comparison, but the difference between list and R6/R6None seems larger for more complex objects:

#     test replications elapsed relative user.self sys.self
# 3   list          100    4.80    1.000      4.45     0.34
# 1     R6          100    5.03    1.048      4.84     0.17
# 2 R6None          100    4.82    1.004      4.59     0.19

Code for the example:

library(data.table)

TestClassNone <- R6::R6Class("TestClassNone",
            portable = FALSE,
            class = FALSE,
            public = list(
              data = NULL,
              sd = NULL,
              sub = NULL,
              initialize = function(data) {
                data <<- data
                get_sd()
                get_sub()
              },
              get_sd = function() {
                sd <<- sd(data[, V1])
              },
              get_sub = function() {
                sub <<- data[1:10]
              }
            ))
TestClass <- R6::R6Class("TestClass",
     public = list(
       data = NULL,
       sd = NULL,
       sub = NULL,
       initialize = function(data) {
         self$data <- data
         self$get_sd()
         self$get_sub()
       },
       get_sd = function() {
         self$sd <- sd(self$data[, V1])
       },
       get_sub = function() {
         self$sub <- self$data[1:10]
       }
     ))

rbenchmark::benchmark("R6" = {
  data <- as.data.table(sample(5e5))
  test <- TestClass$new(data)
},
"R6None" = {
  data <- as.data.table(sample(5e5))
  test <- TestClassNone$new(data)
},
"list" = {
  data <- as.data.table(sample(5e5))
  test <- list(data = data)
  test$get_sd <- function(x) sd(x[["data"]][, V1])
  test$get_sub <- function(x) x[["data"]][1:10, ]
  test$sdd <- test$get_sd(test)
  test$sub <- test$get_sub(test)
},
replications = 100,
columns = c("test", "replications", "elapsed",
            "relative", "user.self", "sys.self"))