Having great tactics in 40k can mean the difference between a win and a loss, but where does your tactical thinking begin? Being able to play tactically begins with army list creation; the units you choose will ultimately affect your in game tactics. The point values you play have a direct affect on how you build your list and what kind of tactics you will be using during your game.
With the advent of 5th and the codex's being geared towards higher point total games (1850+) this means that players are able to run more 'core' units and/or more 'hammer' units. With more units on the table each tactical mistake means less to determine the outcome of the game; simply because you have more units to fall back on. At 2000 points I have the ability to have up to 6 full troop choices (1110pts for six 10 man units of grey hunters in a rhinos); losing one or two hurts a lot less because I have unit redundancy. Another issue that arises with higher point total games is trying to take objectives when your opponent has a horde of troops smothering each objective. Not only are you able to have more ‘core’ units, but you are able to have more ‘uber’ units like the ‘hammers’ and ‘anvils’ and in a lot of cases, the ability to have redundancy with your uber units. In my opinion having the ability to have all of these tools available to you in one list changes the game from having to make every unit count to throwing mass amounts of units at your opponent and hope something sticks.
At 1500 points you are forced to decide between a 'balanced' list and a hammer list because there just isn't enough room for both. Even if you do manage to add a hammer unit to your force it will be relatively small and will only affect the game for two to three turns. With fewer units on the table, you have less to fall back on when you make tactical errors, thus potentially costing you the game. 5th edition has made troops the only units able to claim objectives and at lower point totals each player has to rely on their troops to not only claim objectives but also to take them from your opponent. This makes the tactics for troops vital to your end goal, winning the game. If you make too many tactical mistakes with your troops and they don't survive, the best you can do is play for a tie!
With that being said, the game of 40k relies on tactics no matter what point totals you play at. The next time you sit down for a game or two with your friends, try and challenge your tactical ability and play a smaller point total game.