How to adjust table column parameters in this tabularx correctly?

Question

I am trying to adjust the column parameters but I cannot find a good combination (l/X/p{.1\linewidth}). Adding there X makes the column extremely small in the example code of Fig. 1, which I do not understand. Therefore, I have no X there at the moment. Code which output fails with the last columns, in Fig. 2 without X

\documentclass{beamer}

%http://tex.stackexchange.com/a/309253/13173
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathpazo}
\usepackage[warn]{textcomp}

\usepackage{adjustbox}
\usepackage{tabularx}

\begin{document}

\begin{table}
\centering
\resizebox{.5\textheight}{!}{
\begin{tabularx}{\textwidth}{| l |  p{.27\linewidth} |  p{.27\linewidth} |  p{.27\linewidth} | p{.2\linewidth} |} %
\hline 
\textbf{Feature} & \textbf{Cytotoxic edema} 
         & \textbf{Vasogenic edema} 
         & \textbf{Interstitial edema} 
         & \textbf{Osmotic edema} \\ \hline 
Composition & i/c, acc. of water and Na+
        & e/c, ultrafiltrate of plasma
        & CSF
        & V(e/c) $>$ V(i/c) \\ \hline
Location of edema & Gray-white matter 
          & White - -
          & Periventricular white - - 
          & White - - \\ \hline
V(E/c fluid) & \textdownarrow 
         & \textuparrow 
         & \textuparrow 
         & \textuparrow \\ \hline
Etiology       & DM, hypothermia, ... 
           & Tumors, trauma, ...
           & Hydrocephalus 
           & Hemodialysis, hypertensive crisis, ...\\ \hline
Response to therapy & Yes/No (diuretics transiently eff.)
            & Yes (corticosteroids)
            & Yes (diuretics transiently eff.)
            & Yes/No \\ \hline
\end{tabularx}
}
\caption{Types of brain edema.}
\end{table}

\end{document}

Fig. 1 Output without X, Fig. 2 Output with one X

Answer 1

I would get rid of all vertical lines and most horizontal lines. I would also set the column types ragged-right rather than fully justified. Finally, don't use a table environment -- just place the "caption" in the argument of \frametitle. Observe that the code below by design does not employ \resizebox.

\documentclass{beamer}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usefonttheme{professionalfonts}
\usepackage{mathpazo}
\usepackage[warn]{textcomp}

\usepackage{ragged2e,tabularx,booktabs}
\newcolumntype{Y}{>{\RaggedRight\arraybackslash}X}

\hyphenation{cortico-steroids diu-ret-ics}
\begin{document}

\begin{frame}
\frametitle{Types of brain edema}

\footnotesize
\setlength\tabcolsep{2pt} % default: 6pt
\begin{tabularx}{\textwidth}{@{}
    >{\hsize=0.86\hsize}Y 
    *{4}{>{\hsize=1.035\hsize}Y} @{}}
\toprule
\textbf{Feature} & \textbf{Cytotoxic edema} 
         & \textbf{Vasogenic edema} 
         & \textbf{Interstitial edema} 
         & \textbf{Osmotic edema} \\ 
\midrule 
Composition & i/c, acc. of water and Na+
        & e/c, ultrafiltrate of plasma
        & CSF
        & V(e/c) > V(i/c) \\ 
\addlinespace
Location of edema & Gray-white matter 
          & White - -
          & Periventricular white - - 
          & White - - \\ 
\addlinespace
V(E/c fluid) & \textdownarrow 
         & \textuparrow 
         & \textuparrow 
         & \textuparrow \\ 
\addlinespace
Etiology       & DM, hypothermia, \dots 
           & Tumors, trauma, \dots
           & Hydrocephalus 
           & Hemodialysis, hypertensive crisis, \dots\\ \addlinespace
Response to therapy & Yes/No (diuretics transiently eff.)
            & Yes (corticosteroids)
            & Yes (diuretics transiently eff.)
            & Yes/No \\
\bottomrule
\end{tabularx}

\end{frame}
\end{document}

Answer 2

\begin{table}
\resizebox{\textwidth}{!}{%
  \begin{tabularx}{1.5\textwidth}{| l | X | X | X | X |} %
   ....