Классы или интерфейсы?

public interface IRowViewModel : INotifyPropertyChanged
{
   ISomeItem Item {get;set;}
   string Designation { get;}
   string Name { get;}
}
 
public interface IMaterialRow : IRowViewModel
{
   double Thickness { get; }
}
 
public class SpecMaterialRow : PropertyChangedBase, IMaterialRow
{
   public ISomeItem Item { get; }
   public SpecMaterialRow(ISomeItem _item)
   {
      Item = _item;
   }
 
   public string Designation
   {
      get { return Item.Designation; }
      set { Item.Designation = value;}
   }
   
   public string Name
   {
      get { return Item.Name; }
      set { Item.Name= value;}
   }
   
   public double Thickness => Item.Thickness ;
}

if (rowViewModel is SpecMaterialRow )
  {
      string tempVar = ((SpecMaterialRow) rowViewModel ).Designation;
  }

if (rowViewModel is IMaterialRow  )
  {
      string tempVar = ((IMaterialRow) rowViewModel ).Designation;
  }

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace ConsoleApplication15 {
    class Program {
        static void Main(string[] args) {
        }
    }
    class Horse : Animal {
        public string Name { get; set; }
        public override void Accept(string value) {
            Name = value;
        }
    }
    class Rabbit : Animal {
        public string Color { get; set; }
 
        public override void Accept(string value) {
            Color = value;
        }
    }
    abstract class Animal {
        public abstract void Accept( string value);
    }
}

public class Rabbit : Animal
{
   public string Color { get; set; }
   public Feet Feet { get ; set; } //Лапки
}
 
public class Feet
{
   public bool Fluffy { get; set; }
   pulic Claws Claws { get ; set; } //Когти
}
 
public class Claws 
{
   public bool Sharp { get; set; }
}

var visitor = new ClawsVisitor();
foreach(var animal in animals)
   animal.Feet.Claws.Accept(visitor);

class ConditionalChangerVisitor
{ 
   public void Visit(string name, Rabbit rabbit)
   {
      if (rabbit.Name == name)
         rabbit.Claws.Sharp = false;
   }
}

foreach (var item in shitList)
            {
                item.Accept(program);
            }

var visitor = new ConditionalChangerVisitor(colorForHourse: Color.Yellow);
foreach(var animal in animals)
   animal.Accept(visitor);